Copyright: Copyright © 1993-1999 WinWare Incorporated.


Kryotherm

  ENGINEERING & PRODUCTION FIRM  "KRYOTHERM "
  6 Aerodromnaya street, Saint-Petersburg, 197348 Russia
  tel: 7 (812) 394-1310  fax: 7(812) 394-1267
  Email:  cryotherm @infopro.spb.su    Web:  http://www.kryotherm.spb.ru

  Brief information on thermoelectricity
     What are "Peltier effect" and a thermoelectric module?
      Advantages of thermoelectric modules
      Main fields of thermoelectric modules' application
      About Engineering and Production Firm KRYOTHERM

  General information about the program
      How to use the program
      Designations
      How to use the keyboard and the mouse
      Print

 Performance Graphs
      The standard graphs
           The general data about the standard graphs
             Graph 1
             Graph 2
             Graph 3
             Graph 4
             The example of the calculation by the standard graphs
      The detailed graphs
             The general data about the detailed graphs
             Type 1
             Type 2
             Type 3
             Type 4
             Type 5
             The example of the calculation by the detailed graphs

Choice of modules
        Initial data
             Cooling capacity calculation
                  Geometry of the object
                  Load
                  Insulation
                  Cooling mode
                  Results of cooling capacity calculation
        Optimization, sorting and view of the variants
        Variants of solution for the task of cooling
       Graphs
              Standard
              Detailed
       Additional information

 Thermoelectric System Calculation
       The process of thermoelectric system calculation
       The thermal model of thermoelectric system
       Initial data for thermoelectric system calculation
              Selecting of modules, connection scheme and power source
              Insulation thermal resistance calculation
              The hot side and the cold side parameters determination
                     Intermediate thermal resistance calculation
                     Heat exchanger thermal resistance calculation
          Heat emission coefficient calculation
               Ambient and object heat rejected
       Thermoelectric system calculation results


What are "Peltier  effect" and a thermoelectric module?

      The work principle of a thermoelectric module is based on Peltier effect discovered in 1834. As an electric current passes through a circuit consisting of heterogeneous conductors (thermocouple), heat is released or absorbed at conductors' contracts depending on current directions. Heat quantity is in direct proportion to the current passing through the thermocouple.
        Peltier effect is especially efficient when used to manufacture thermocouples with semiconductors of different conductivity type (of n- and p- type). The Engineering and Production Firm KRYOTHERM uses tellurium-bismuth alloy with additions of selenium and antimony. Thoroughly cleaned and prepared materials are fused together to obtain a polycrystalline material with anisotropic thermoelectric properties. Long-term  experience in research in the field of semiconductor materials enables engineers of the KRYOTHERM to design high-quality thermoelectric materials and to achieve unique characteristics in serial production.
        Ingots of alloyed materials are sliced into rectangular pellets with a square cross-section. Two serially joint pellets of different conductivity form a thermocouple. Thermocouples are serially connected (parallel to the heat flow) between two ceramic plates to produce a thermoelectric module.

Back


Advantages of thermoelectric modules

       Cooling devices based on thermoelectric modules play the same role as a traditional compressor or absorbing units used in refrigerators operated by cooling agents.  However, the application of thermoelectric modules that actually are solid-state heat pumps, offers a number of the following advantages:
     · Absence of moving parts or working fluids in a cooling unit;
     · Noiseless operation;
     · Small size and weight of a cooling system. A possibility to install miniature coolers;
     · High reliability of a thermoelectric module (the Engineering and Production Firm  KRYOTHERM guarantees the mean time between failures (MTBF) not less than  200,000 hours);
     · Easy operating and possibility of precise temperature regulation;
     · Cost-effectiveness;
     · Possibility of operation in any position.
       These advantages make thermoelectric modules very popular that is confirmed by increasing demand on the world market and new fields of application for them. Even if these factors are not primary, thermoelectricity can not be seen as a single solution to all cooling issues. That is why when choosing a cooling system for a specific task one should use such criteria as "cost - effectiveness".

Back


Main fields of thermoelectric modules' application

      Within a variety of application areas there is a certain range of fields where the thermoelectric modules can be used:

Radio - electronics
       Miniature cooling units for incoming stages of highly sensitive receivers and amplifiers, coolers for high - power generators and radioelements, laser emitters and systems, CCD cameras and matrixes, parametric amplifiers of various applications, vacuum and solid-state photodetectors (photodiodes, phototransistors, photoamplifiers), CPU coolers, electronic boards and units.

Medicine
       Mobile cooling containers for storage of biologic tissue and liquid (blood, lymph, biological solutions), ophthalmologic devices for crystallic lens transplantation, micropincers, cooling blankets and sheets, devices for treatment and preventive maintenance of skin diseases, anaesthesiologic equipment, cosmetic and pharmaceutical items.

Scientific and Laboratory Equipment
       Cooling chambers and freezers, temperature stabilised chambers, cold laboratory plates and tables, thermocalibrators,  stage coolers, thermostats, coolers and temperature stabilisers for multipurpose sensors (in a number of cases thermoelectric modules are used directly as sensors).

Consumer Goods
       Portable refrigerators of various size and application (picnic boxes), drinking water and beverage coolers, cooling boxes and cabinets for stores and cafes, coolers for motorcycle helmets, wine coolers, massage equipment.

Climate Devices
       Multipurpose thermoelectric conditioners, airflow cooling fans, room air conditioner-humidifiers for electronic racks, cabinets, libraries and video libraries, temperature stabilisers for aquariums and terrariums.

Back


About the Engineering and Production Firm KRYOTHERM

      The firm was founded in 1992 as a result of the governmental privatisation program. It was based in the biggest research and development institute, dealing with thermoelectric modules and systems for the needs of the army and the aerospace industry. Thanks to the great scholarly potential and application of the modern management techniques since the beginning the firm has taken the leading position on the world thermoelectric market.
       A marketing strategy to provide all our customers the high-quality production, the best services and full technical maintenance is the essence of the activities carried out by the Engineering and Production Firm KRYOTHERM.
       The firm permanently widens and improves the range of the manufactured goods. By now it produces more than 150 types of thermoelectric modules. One of the major fields of the firm's activity is the development and production of thermoelectric modules and related systems according to the special requests of our customers. This approach enables us to offer the most effective solution based upon the 35-years experience of our engineers and researchers in different areas of thermoelectricity.
       We also carry on improving the quality and characteristics of our products, not only widening their range, but also preserving competitive prices on the world market. Technical characteristics and the quality of thermoelectric modules of the Engineering and Production Firm KRYOTHERM entirely meets the world standards' requirements.
       For further information on the firm's activities go to our website: http://www.kryotherm.spb.ru

Back


How to use  the program

     We are glad to introduce you the program "Kryotherm". The goal of our program is to answer lots of the questions that arise to the designers of the cooling systems based on the thermoelectric modules and to all who is interested in this promising technical direction. Contacting our clients for many years we selected the most popular questions what our specialists were asked. They are:
     1. How does the thermoelectric module work?
     2. How many and what type of modules should be used?
     3. What sort of effect will the use of the thermoelectric modules have on the cooling system characteristics?
       Being ruled by the wish  to answer the questions as full as possible we created the computer program called "Kryotherm". It consists of the following parts:
     1. Performance Graphs
     2. Choice of modules
     3. Thermoelectric system calculation

Performance Graphs
       We recommend to address to this program part if you would like to clear up the peculiarities of the behavior of a particular module's parameters. It allows to estimate the possibilities of the chosen thermoelectric module with the help of standard or detailed graphs.
       Standard graphs allow to observe the general characteristics' alternation. In this section you will find such important information as cooling capacity dependence on the temperature difference between the module's sides. The other section called "Detailed Graphs" allows to estimate a behavior of various characteristics  at some fixed conditions.

Choice of Modules
       If you are going to start the working out of the cooling system based on the thermoelectric modules, then it is worth to pay your attention to the program part called "Choice of Modules". With its help you will be able to get the necessary information about the parameters of the thermoelectric modules and the recommendations about their application for the cooling purposes.
       At the first stage of the thermoelectric system projecting it is necessary to determine the parameters it should run at. These parameters are the ambient temperature, the temperature of cooled object and the cooling capacity. The cooling capacity value can be calculated with the help of our program if the characteristics of the insulation are known.
       On the analysis basis of the initial data you will get the answer to the following question - how many modules and of what types it is necessary to use in the cooling system. We will indicate you some other values as well. For each variant we offer the parameters' plots and the additional information. This will allow you to get the more entire notion about the work of the thermoelectric cooling system.

Thermoelectric system calculation
       The third part of the program called "Thermoelectric system calculation" will help to calculate the characteristics provided by the determined cooling system using the thermoelectric modules.
       The main purpose of the calculations is to find the temperature of the cooled object, for example, the temperature inside the camera of thermoelectric fridge.
The general parameters of the cooling system's elements must be known. It is necessary to input the following values:
     · type, quantity of modules and electric scheme of the connection;
     · the insulation thermal resistance;
     · type of cooling (Natural, Forced, Flow) on the hot and cold sides and thermal resistances of the sides;
     · heat released in the object;
     · the ambient temperature;
     · voltage or current of the power supply.
       In the case when the "Flow" type of cooling is chosen it is also necessary to determine the flow rate value and the flow temperature at the inlet. The program will calculate the outlet flow temperature.
       If you have any complications with the initial data, we can help you to determinate them by the optional algorithms. The optional algorithms may be also used only for thermophysical calculations (calculations of heat sinks, insulation).
       Our program will introduce the detailed results of calculations - the temperature of the cooled object, the temperature field in whole thermoelectric system, energetic parameters, the coefficient of performance.

       Thus the program "Kryotherm" allows to make the detailed and complete calculations of the thermoelectric modules and system on their basis. If you have any questions, please, do not hesitate to contact us and you will receive all necessary information.

Back


Designations

Consumer parameters
dTmax - the maximum temperature difference between the sides of the module at the determined hot side temperature (Th=300 K) (K);
Imax - current, at that the maximum temperature difference dTmax  is obtained (A);
Umax - voltage, corresponding to current Imax and temperature difference dTmax (V);
Qmax - cooling capacity at the current I=Imax and temperature difference dT=0 (W).

Quantity of the modules
n - total quantity of the modules;
ns and np - the number of modules in each group and the number of groups
(in case of series-parallel connection scheme), ns*np=n.

Energetic characteristics
I - current (A);
U - voltage (V);
W=I*U - electric power consumption (W);
Qc - cooling capacity (W);
Qh=Qc+W - heat released on the hot side (W);
COP=Qc/W - coefficient of performance;
Wob - heat released in object (W).

Thermal resistances
Rc=(Tob-Tc)/Qc - thermal resistance between the object and the cold surface of thermoelectric module (K/W);
Rh=(Th-Ta)/Qh - thermal resistance between the hot surface of thermoelectric module and the ambient (K/W);
Rc1 and Rh1 - heat exchangers thermal resistances per one module at the cold and the hot sides of thermoelectric system (K/W);
Rc2 and Rh2 - intermediate thermal resistances at the cold and the hot sides of thermoelectric system (K/W);
Rins - insulation thermal resistance (K/W).

Temperatures
Tob - the temperature of the object to be cooled (K);
Ta - the ambient temperature (K);
Tc - the cold side temperature of the thermoelectric module (K);
Th -  the hot side temperature of the thermoelectric module (K);
dT=Th-Tc - the temperature difference between the module's sides (K);

Flow characteristics
Tcf0 and Thf0 - inlet flow temperatures at the cold and hot sides of thermoelectric system (K);
Tcf1 and Thf1 - outlet flow temperatures at the cold and hot sides of thermoelectric system (K);
Tcfa and Thfa - average values of flow temperature at the cold and hot sides of thermoelectric system (K);
dTcf=Tcf0-Tcf1 - difference between inlet and outlet cold flow temperatures (K);
dThf=Thf1-Thf0 - difference between outlet and inlet hot flow temperatures (K);
Wc=Qc/dTcf - cold flow equivalent (W/K);
Wh=Qh/dThf - hot flow equivalent (W/K).

Back


How to use the keyboard and the mouse

       In the parts "Performance Graphs" and "Choice of Modules" of the program "Kryotherm" any of the standard and detailed graphs can be widened up to the sizes of the whole screen. For that it is necessary to bring the mouse pointer to the graph of your interest and press twice the left mouse button. To return to the previous window one needs to press the combination of the keys Alt+C.
       Any of the graphs can be considered in more details if to mark the field of your interest with the help of the mouse. For that it is necessary to press the key Shift and the left key of the mouse and, not releasing it, to mark the rectangular frame. To return to the graph of the normal sizes one needs to press Shift and the left button of the mouse.
       In the program part "Choice of Modules" the display of additional information by each variant of the decision of the cooling task is provided. To get the additional information click twice the left mouse button at the results table.
       You can call context help by pressing key F1.

Back


Print

       Our program allows printing of initial data, graphs and results of calculating. By pressing button "Print" or by choosing corresponding menu point you can make preview and printing of all necessary information.
       The printing is possible, if you have a default printer.

Back


The general data about the standard graphs

       The window with the standard graphs appears after the choice of the module and pushing of the button "Standard". The name of the module is in the upper line on the left. Further there are the consumers' parameters of the module - Imax, Qmax, Umax, dTmax. The consumers' parameters of the module depend on the temperature of the hot side Th. The value of the temperature  Th is entered in the window down on the left. At the temperature Th=300 К these parameters correspond to the data, given in the company "Kryotherm" catalogue.
       The standard graphs are four universal functions, which one should use for the calculations of the characteristics of the thermoelectric modules. These functions are the ones of the cooling capacity, voltage and COP vs. the difference of the temperatures between the module's sides (graphs № 1-3), and also the function of the voltage vs. the current (graph № 4).
       The standard graphs № 1-3 are plotted at four specific values of the current. The currents are indicated in the rates from Imax. In the legend of the broadened graph these values are indicated in Amps.
       The standard graph № 4 is plotted at four specific values of the difference of the temperatures. The differences of the temperatures are indicated in the rates from dTmax. In the legend of the broadened graph these values are indicated in Kelvin.

Back


Graph 1
Standard graphs - graph 1

       The standard graph № 1 is the function of the cooling capacity vs. the temperature difference between the hot side and the cold one of the thermoelectric module. This function is plotted at the fixed values of the current.
       This graph is the most important. With its help one can determine, how much of the thermal energy can be transferred by the module from the object which is being cooled at the set difference of the temperatures between the sides of the module.
       At the supplying of the thermal load to the thermoelectric module this thermal energy heats the cold side, as the result of  it the difference of the temperatures between the sides of the module reduces. At the absence of the thermal load the module develops the maximum difference of the temperatures.
       As the current increases Peltier effect is shown stronger, and the curves move aside the larger values of the temperature differences and larger cooling capacities.

Back


Graph 2
Standard graphs - graph 2

       The standard graph № 2 is the function of the voltage, supplying to the thermoelectric module, vs. the difference of the temperatures between the hot side and the cold one. This function is plotted at the specific values of the current.
       The voltage, applying to the module, consists of two parts - Ohm voltage and the voltage spent for the overcoming of electromotive force (EMF), which appears in the result of Seebeck effect. At the fixed value of the current the Ohm part is constant, and the voltage of Seebeck linearly depends on  the difference of the temperatures between the sides of the module. For the achieving of the larger difference of the temperatures it is necessary to apply the larger voltage to the module.

Back


Graph 3
Standard graphs - graph 3

       The standard graph № 3 is the function of the coefficient of performance vs. the temperature difference between the hot side and the cold side of the thermoelectric module. This function is plotted at the specific values of the current.
       The coefficient of performance is the ratio of the cooling capacity to the electric energy, consumed by the module. At the fixed value of the current the electric energy, which is being consumed by the thermoelectric module slightly enlarges at the increasing of the temperature difference, and the cooling capacity decreases linearly at the increasing of the temperature difference. As the result COP decreases at the increasing of the temperature difference.
       At the little currents the module consumes  small quantity of the electric energy, and, therefore, the efficiency of its work  (COP) turns out to be higher, than at the large currents. However, at the large currents the Peltier effect is shown stronger, and the deeper cooling can be achieved.

Back


Graph 4
Standard graphs - graph 4

       The standard graph № 4 is the function of the voltage, supplying to the thermoelectric module, vs. the current. This function is plotted at the specific values of the temperature difference between the module's sides.
       The voltage, applying to the module, consists of two parts - Ohm voltage and the voltage spent for the overcoming of EMF, which appears in the result of Seebeck effect. At the fixed value of the temperature difference the Seebeck part is constant, and the Ohm part is directly proportional to the current. As the result the voltage linearly increases in the dependence of the current.

Back


The example of the calculation by the standard graphs

       To cool optimally  the object with the help of the thermoelectric module it is necessary to know the thermal power, releasing in the object, the temperature up to which the object should be cooled, and also the environment temperature. On knowing these values, one can estimate the required cooling capacity, and the temperatures of the hot side and the cold side of the thermoelectric module.
       For the cooling up to the set temperature and the heat removal from the object it is necessary to apply the specific voltage to the module (to pass through it the specific current). It is also useful to know the coefficient of performance.
       The principle of the determination of the module's characteristics is shown in the following example:
     Let us choose the module TB-127-1.4-1.5. The cooling capacity should have the value Qc=20 W,  the temperature of the module's sides - Th=293 K (20 °C) and Tc=255 K (-18 °C).The operating current, the operating voltage, COP should be determined.
The sequence of the calculation:
     1. Choose module TB-127-1.4-1.5 and push button "Standard".
     2. In the down left corner of the screen set the temperature of the hot module's side Th=293 K.
     3. Calculate the temperature difference - dT=Th-Tc=293-255=38 K.
     4. With the help of the standard graph № 1 find the current so that at the difference of the temperatures dT=38 K to provide the cooling capacity Qc=20 W. This current is equal to I=0.74*Imax or I=4.4 A.
     5. With the help of the standard graph № 2 (or standard graph № 4) find the voltage, which corresponds to the current I=4.4 А and to the difference of the temperatures dT=38 K. This voltage is equal to U=10.9 V.
     6. With the help of the standard graph  № 3 one can find COP, corresponding to the current I=0.74*Imax and the difference of the temperatures dT=38 K. The coefficient of performance is equal to COP=0.42.

Back


The general data about the detailed graphs

       The window with the detailed graphs appears after the choice of the module and the pushing of the button "Detailed". The name of the module is given in the upper line on the left. Further the consumer's parameters of the module are given - Imax, Qmax, Umax, dTmax, calculated at the temperature Th=300 K.
       The detailed graphs are the set of the functions of the characteristics of the chosen module at two fixed parameters. The fixed parameters are  Tc, Th, Qc, W. In the accordance with the possible choice of two parameters the detailed graphs are separated into the following types:
     type № 1 - Qc=const, Th=const;
     type № 2 - Qc=const, Tc=const;
     type № 3 - Tc=const, Th=const;
     type № 4 - Tc=const, W=const;
     type № 5 - Th=const, W=const.
     The choice of the type is made in the upper part of the window with the detailed graphs. The values of the parameters are set in the right down corner.
     In each type of the detailed graphs there are four groups of the graphs, describing the different parameters.

Back


Type 1
Detailed graphs - type 1

       Detailed graphs of the type № 1 are plotted with the fixed values of the cooling capacity Qc and temperature of the hot side Th. This situation occurs when the object that is being cooled possesses the stable power of the thermal fluxes and when the temperature of the environment is known. Depending on the power of the thermal fluxes and temperature of the environment one can evaluate the needed cooling capacity as well as the temperature of the hot side of the thermoelectric module.
       Assigning numerical values of the Qc and Th one can obtain the graphs of the following functions:
     group № 1 - Tc vs. I, U, W;
     group № 2 - COP vs. I, U, W;
     group № 3 - Qh vs. I, U, W;
     group № 4 - U vs. I, W vs. I, W vs. U;
      The essential graph of the type № 1 is the graph Tc=f(I) of the first group. It allows to define what current one should pass through the thermoelectric module to cool the object up to the necessary temperature.
       From the graph one can see that there is the value of current at which the maximum cooling can be obtained. At the values of the current lower then optimal ones Peltier effect does not manifest sufficiently and reached cooling is less then maximum possible. At the greater values of the current the temperature of the cold side increases by the reason considerable releasing of the Joule energy.

Back


Type 2
Detailed graphs - type 2

       The detailed graphs of the type № 2 are plotted with the fixed values of the cooling capacity Qc and temperature of the cold side Tc. This situation occurs when the object that is being cooled should be maintained at the particular temperature  and when this object possesses stable power of thermal releasing.
       Depending on the power of the thermal fluxes and required temperature of the object one can evaluate the needed cooling capacity as well as the temperature of the cold side of the thermoelectric module. Assigning numerical values of the Qc and Tc one can obtain the graphs of the following functions:
     group № 1 - Th vs. I, U, W;
     group № 2 - COP vs. I, U, W;
     group № 3 - Qh vs. I, U, W;
     group № 4 - U vs. I, W vs. I, W vs. U;
       The essential graph of the type № 2 is the graph Th=f(I) of the first group. It allows to evaluate what should be the temperature of the hot side for the indicated conditions could be provided. The high value of the temperature of the hot side  allows to get considerable overheat in comparison with the environment. Under the stable released heat Qh the greater overheat contribute to the better removing of the thermal energy from the hot side of the thermoelectric module.
       From the graph one can see that there is the value of current at which the maximum temperature of the hot side can be reached. At the value of the current less then optimum one the module does not show maximum possible difference of the temperatures by the reason of insufficient manifestation of the Peltier effect. But with large value of the current the difference of the temperatures  is less them maximum due to the considerable releasing of the Joule energy.

Back


Type 3
Detailed graphs - type 3

       The detailed graphs of the type № 3 are plotted with the fixed values of the temperatures of the cold Tc and hot Th sides of the module. This situation occurs when the temperature at which the cooling object should be maintained and the temperature of the environment are known. Depending on these temperatures one can evaluate the temperatures of the sides of the thermoelectric module. Assigning numerical values of the Tc and Th one can obtain the graphs of the following functions:
     group № 1 - Qc vs. I, U, W;
     group № 2 - COP vs. I, U, W;
     group № 3 - Qh vs. I, U, W;
     group № 4 - U vs. I, W vs. I, W vs. U;
       The essential graphs of the type № 3 are the graph Qc=f(I) of the first group and the graph COP=f(I) of the second group. It allows to evaluate what current should be passed through the thermoelectric module to provide the maximum cooling capacity or maximum cooling coefficient. From the graph one can see that there are such values of current at which these parameters have the maximum values.

Back


Type 4
Detailed graphs - type 4

       The detailed graphs of the type № 4 are plotted with the fixed values of the temperature of the  cold side Tc and power consumption W. This situation occurs when the temperature at which the cooling object should be maintained and power consumption are known (for example, there is a limitation to the source of the power).
       Assigning numerical values of the Tc and W one can obtain the graphs of the following functions:
     group № 1 - Th vs. I, U, Qh;
     group № 2 - Qc vs. I, U, dT;
     group № 3 - Qh vs. I, U, dT;
     group № 4 - COP vs. I, U, dT;
       The essential graph of the type № 4 is the graph Qc=f (I) of the second group.
It allows to evaluate the cooling capacity that can be provided under the indicated temperatures of the sides of the module and consuming power. From the graph one can see that with the increasing of the temperature difference dT (i. e. growing of the hot side temperature) the cooling capacity decreases.

Back


Type 5
Detailed graphs - type 5

       The detailed graphs of the type № 5 are plotted with the fixed values of the temperature of the cold side Tc and power consumption W. This situation occurs when the ambient temperature and consuming power are known (for example, there is a limitation to the source of the power). Assigning numerical values of the Th and W one can obtain the graphs of the following functions:
     group № 1 - Tc vs. I, U, Qc;
     group № 2 - Qc vs. I, U, dT;
     group № 3 - Qh vs. I, U, dT;
     group № 4 - COP vs. I, U, dT;
       The essential graph of the type № 5 is the graph Tc=f(Qc) of the first group. It allows to evaluate the temperature of the cold side depending on the cooling capacity. From the graph one can see that with the increasing of the temperatures difference  (i. e. with the decreasing of the temperature of the cold side) the cooling capacity lessen.

Back


The example of the calculation by the detailed graphs

       To cool the object optimally by means of the thermoelectric module it is necessary to know the thermal power, which is releasing in the object, the temperature up to which the object should be cooled and the environment temperature. On knowing these values one can evaluate the necessary cooling capacity and the temperature of the hot and cold sides of the thermoelectric module.
       For the cooling up to the particular temperature and heat transfer it is necessary to apply specific voltage (to pass through the thermoelectric module specific current). Due to the graphs one can also determine COP and other characteristics of the thermoelectric module.
       One of the variants of the thermoelectric module characteristics determination is shown in the following sample:
       Let us choose the thermoelectric module TB-127-1,4-1,5. The temperatures of the sides of the modules are Th=293 K (20 °C), Tc=255 K (-18 °C).
       One should find the maximum value of COP and corresponding to it characteristics.
The sequence of calculation is following:
     1. Choose the thermoelectric module TB-127-1,4-1,5 and press the button "Detailed".
     2. On the base of the initial data choose the type of the graph. In this case you should use the detailed graph of the type № 3.
     3.  Enter the initial data - Tc=255 K, Th=293 K.
     4. At the graph COP=f(I) of the group № 2 find maximum value COP=0.48 and corresponding to it operating current I=3.4 A.
     5. At the graph Qc =f(I) of the group № 1 find the cooling capacity  Qc=14.2 W, which corresponds to the operating current I=3.4 A.
     6. At the graph  Qc=f(U) of the group № 1 find the operating voltage U=8.8 V,  which corresponds to the cooling capacity Qc=14.2 W.
     7. At the graph Qc=f(W) of the group № 1 find the consuming power W=29.8 W, which corresponds to the cooling capacity Qc=14.2 W.
     8. At the graph Qh=f(I) of the group № 3 find the cooling capacity Qh=44.0 W, which corresponds to the operating current I=3.4 A.

Back


Initial data

      Our program will choose the modules, which are the most appropriate to your thermoelectric cooling system. You should only assign defined input data set - ambient temperature (Ta), temperature of the object (Tob), cooling capacity (Qc), and also thermal resistance on the cold side of cooling system (Rc).
       Cooling capacity value  Qc is total heat power, which is absorbed on the cold side of thermoelectric modules. If you are unable to indicate exact value of cooling capacity, but you know parameters of the object and it's working mode, it is possible to use appropriate menu point or button for calculation of this value.
       Rc value characterizes total thermal resistance between the object and cold side of all thermoelectric modules. As the first degree approximation we can accept, that thermal resistance on the cold side is equal to zero. If you have already decided, how  heat transfer from the object to the modules will be realized, you should set summary value of thermal resistance of selected heat sinks.
       Also, you can indicate, by which way the system's  hot side will be cooled. Heat transfer from the hot side of thermoelectric modules can be realized through the natural or forced convection, and also with the help of liquid flow. Choosing the variant of module's application ,  we will certainly consider your desires as the thermal resistance value Rh. The most simple way is using of air cooling, but, under this conditions temperature difference on the heat sink may be rather significant, and efficiency of module's work will reduced. In this case it is necessary to take steps and make temperature difference not more than 15 K.
       Proceeding from the initial data, the temperatures of the module's sides Tc and Th will be calculated.

Back


Geometry of the object

      To determine cooling capacity of the object it is necessary to assign object's geometry, i. e. to determine its shape and dimensions. Using radio-buttons, you can choose one of the shapes (box or cylinder), which is appropriate to your object. Than, you should set internal dimensions of your object. For the box it will be width Wi,  height Hi and length Li,  for the cylinder - height Hi and diameter Di.

Back


Load

      As the load Wob we understand heat power released in the object, which has to be removed with the help of thermoelectric modules. If there is no heat release in the object, you should select passive load. In the opposite case, select active load and assign numerical value of heat power, which is released in the cooling object.

Back


Insulation

      In order to keep the object temperature Tob lower, that the ambient temperature Ta, it is efficiently to apply thermal insulation of the object. We offer list of materials, which are usually used as insulators. If you prefer another insulator, you should set value of thermal conductivity, typical for this material. Also it is necessary to set the value of insulation thickness th.

Back


Cooling mode

      Very often it is necessary to cool object till defined temperature for the defined time, in another words we speak about non-stationary mode. In this case you should indicate time, which you need to cool the object from Ta till Tob, and also, please, set material's characteristics - its density and specific heat. For the most popular materials you can find list of these characteristics.

Back


Results of calculation
Results of cooling capacity calculation

      As the result of calculation we will determine requested cooling capacity Qc. On the base of this value it will be possible to select thermoelectric modules, suitable for cooling system.
       In case of stationary mode, it is necessary to keep value of cooling capacity Qc constant in time. In case of non-stationary mode , you should keep value of cooling capacity Qc within prescribed time of cooling. After this time object attains temperature Tob, and in future it is requested to keep less value of cooling capacity - cooling capacity in stationary mode Qstat. In non-stationary mode value Qc tends to the value of Qstat, if time of cooling tends to infinity.
       As the result of calculation you can see the value of thermal resistance between the object and environment Rins, and also internal volume of the box or cylinder.

Back


Optimization, sorting and view of the variants

     We introduce list of all thermoelectric modules, which could help to provide assigned demands for the cooling system, and their optimal characteristics. Task of variant's selecting for thermoelectric cooling system is solved in one of two modes - maximal COP or minimal cost of the modules. The main feature of maximal COP mode is increased efficiency of the work, but in this case we need rather big quantity of the modules. In the mode of minimal cost, the task can be solved by using of small quantity of modules, but value of COP is reduced.
       For any selected optimization you have possibility to view variants in those order, which is introduced in Catalogue of EPF "Kryotherm", or sort them according to optimized parameter (COP or modules' cost).
       Depending on your desire, you can view top 5, 10 or all variants of solution of the task. Also, there is possibility of data display and data print-out for any quantity of variants. In this case you should assign start and final position of list of solutions. Use of unsorted list allows to view separate groups of the modules.

Back


Variants of solution for the task of cooling

      The program offers variants of application for all thermoelectric modules of firm "Kryotherm", which can satisfy designed cooling conditions.
       You should use any module in quantity m pieces, and for cases of optimization for COP and for minimal cost - different values  m will be offered. Each variant indicates value of COP.
       Operating voltage U (Volts) needs to be applied on each module, and operating current I (Ampers) should flow through each module. W (Watts) - electric power, which is consumed by the module from the source.
       Qh (Watts) - heat power, which is released on the hot side of thermoelectric module. To remove this power it is recommended to have heat exchanger with thermal resistance Rh (K/W) or with the less value, for each module.

Back


Standard
Standard graphs

      In the part "Choice of Modules" the program provides construction of the graphs, analogues to those, which are used in part "Performance Graphs". It is possible to construct standard graphs for every variant.
       These dependencies are calculated proceeding from the parameters of chosen module and have following singularities:
     - All graphs are plotted on the fixed value of Th;
     - Standard graphs are plotted on the one fixed value of current I;
     - Standard graph № 4 is plotted on the one fixed value of temperature difference between hot and cold sides of the module.
     - All characteristics on standard graphs are introduced for one module
       In the other - graphs of both parts of the program are analogues each other.

Back


Detailed
Detailed graphs

      In the part "Choice of Modules"  the program provides plotting of the graphs, analogues to the ones in the part  "Performance Graphs". You have possibility to design detailed graphs for every variant of application of thermoelectric modules.
       These dependencies data are calculated proceeding from the parameters of chosen module and have following singularities:
     - All graphs are plotted on the fixed values of Th, Tc, Qc, W.
     - All characteristics of the detail graphs are introduced for the one module.
       In the other - graphs of the both parts are analogues each other.

Back


Additional information

      To open additional information you should click twice the left button of the mouse and in this window you will find useful information for each variant of application for thermoelectric modules of the company "Kryotherm".
       In the block "Initial Data of the Task and Temperatures" you can find initial parameters of the task - temperature of environment Ta and temperature of the object Tob, cooling capacity Qc, thermal resistance Rc and also way of cooling, sorting mode and variant's optimization mode.
       Proceeding from the initial data, the temperatures of the hot side Th and the cold side Tc and their difference are calculated.
       In the block "Solution" it is showed name of the module, number of it's position in the  list of solution and optimal quantity of the modules n.
       In the block "Thermoelectric Module Parameters" the program introduces optimal parameters for one and for n modules - cooling capacity, consumed power, operating current, operating voltage, and COP.
       In the block "Parameters for Heat Exchangers Design" it is introduced characteristics for design of heat sinks. You can see values of thermal resistance on the cold side of cooling system, calculating for one and m modules. Also there is recommendation to use heat sink with defined value of thermal resistance or the less value, for the hot side of the module. It is indicated quantity of heat power, which is need to be removed from the hot side, and also module's area and density of heat flow on the hot surface. It is shown value of heat emission effective coefficient. Effective coefficient of heat emission numerically equal to  the value of heat emission coefficient, which is need to be provided for removing of the heat flow from the non-rib surface of the modules.
       Maximal values of heat emission coefficient are approximately equal to 10 W/(m^2*К) at the natural convection, 100 W/(m^2*К) at the forced convection in the air and 3000 W/(m^2*К) at the forced convection in the water. Comparing these values and value of effective coefficient of heat emission, we can make a conclusion about possibility of application  of any way of cooling.
       It is necessary to take into account, that area of rib surface of the heat sink is significantly more than area of the base. Accordingly, the real value of heat emission coefficient on the rib surface can be by an order less than the value of heat emission effective coefficient.
       You should make a choice of  heat sink of hot side, proceeding from two characteristics - area of the modules and value of thermal resistance. From the catalogs you can find heat sinks with area, equal to, or little bit more than area of the modules. Than, you should chose those types, which have the least value of thermal resistance.

Back


The process of thermoelectric system calculation

      "Thermoelectric System Calculation" program is designed for the calculation of the characteristics of the particular thermoelectric cooling system.
       The parameters of the system construction are supposed to be defined. The main aim of the calculation is to determine the temperature of the cooled object as well as other temperatures and energetic characteristics of the system.
       Any thermoelectric system can be divided into the three parts - modules, cold side and hot side. Such dividing allows to consider the characteristics of every element of the cooling system separately, and construction calculation becomes easier.
       At the beginning of the calculation it is necessary to define the type and quantity of the modules to use. For not very sophisticated systems  usage of one or two modules is sufficient. As soon as you have chosen some modules, you may specify the scheme of their connection taking into account the number of the modules.  It is also necessary to define the value of the current or voltage for the cooling system power source.
       The processes of the heat transmission from the object to the cold side of the module and from the hot side of the module to the ambience is made by means of heat exchanger. One should specify the type of cooling and thermal resistances of the hot and cold sides. The program offers the following type of the cooling: Natural convection (cooling by means of heat sink),  Forced convection (cooling by means of heat sink and fan), and Flow (cooling of liquid/gas flow).
       In case you choose the "Flow" regime of cooling, it is necessary to input its  temperature at the inlet and its rate of flow.  At the setting of Flow at the cold side the main result of the calculations will be the temperature of the flow at the outlet Tcf1.
       Thermal resistance of the sides is calculated for one module and is the sum of the intermediate thermal resistance (thermal grease, heat conductor) and the thermal resistance of the heat exchanger (heat sink).These values can be calculated with the help of our program. Thermal resistance of the heat sink depends on its dimensions, material and the heat emission coefficient. The program possesses special algorithm that allows to calculate the heat emission coefficient.
       The next step is to define ambient temperature and power of the heat released at the object. Then one can start the calculation of the parameters of the thermoelectric system pressing the button "Calculate system". You will get the detailed results of the calculations - temperature range in the thermoelectric system  and energetic characteristics.
       In case you are not satisfied with the results of the calculations, for example insufficient temperature of the object, you can repeat the calculation with the other initial data. Moreover, try to analyze the results of the calculations and gather what element of the system is to be improved in first turn. For example, if the temperature difference between the hot side of the module and ambience Th-Ta is more than 25 degrees, the thermal resistance at the hot side will be too big you should pay more attention to the choice of the heat exchanger. With the help of this program you will surely find the required parameters of the cooling system to fulfil your task and provide  the required level of cooling.

Back


The thermal model of thermoelectric system

       Calculation of the heat regime of the cooling system based on the thermoelectric modules is quite a serious scientific task. It is caused by several reasons i. e. system construction peculiarities, considerable number of outward factors influencing the system, variety of the originating processes.
       At the designing of the program we constructed  and realized  the thermal model of the thermoelectric system that is easy and convenient in running and at the same time reflects basic regularities of the real phenomena. Thus, in this thermal module some secondary factors were omitted. Please, pay attention to the made essential admissions:

Stationarity
       This part of the program allows to calculate only stationary regimes of the thermoelectric devices running. If you are interested in the dynamic regimes, please, contact us and our high level specialists will offer you possible solution for your task.

One-dimentionality
       Spreading of the heat along the elements of the thermoelectric system construction is described by the three-dimensional thermal conductivity equations, as its detailed calculation is quite difficult. In order to simplify the task, the main direction of the heat spreading in the thermoelectric cooling system is defined. In other directions heat spreading is not so considerable. Thus, their values can be omitted.
     Our program deals with the one-dimentionality of the heat spreading excluding follows cases:
     · the program allows to input the coefficient of the temperature irregularity along the base of the heat sink and thus, take indirectly into account  double dimentionality of the temperature field.
     · the program allows to calculate cooling systems when the flow of gas or liquid at the one of the side is chosen. In this case the value of the temperature difference between the flow and base of the heat sink is supposed to change along the length of the heat exchanger. This change is of exponential character. Moreover, the program allows to define the flow temperature at the outlet knowing the inlet flow temperature.

Heat Transfer
       The program deals only with two ways of heat transfer where thermal conductivity and convection is considered. The process of the heat transfer by means of irradiation is not considered.

Outward factors
       Among numerous outward factors  influencing the cooling system calculation takes into account only ambient temperature, while humidity, pressure, electromagnetic field and others factors are omitted.

Modules
       The possibility of the thermoelectric modules' parameters change at the temperature fluctuation from the normal is not considered. Thermoelectric modules are manufactured on the base of semiconductor materials and their features can change considerably depending on the temperature fluctuation.
       Also we do not consider the temperature drop  on the ceramic plates of the modules. The thickness of the ceramic plates that we use is approximately 1 mm. The value of the coefficient of thermal conductivity of the ceramics is approximately equal to 25 W/(m*K). The value of the thermal resistance of the ceramics is less than thermal resistance of the grease and other elements of the construction, thus at the first sight, temperature drop on the ceramics can be omitted. If it is still necessary to consider the thermal resistance of the ceramics, for example, at the high heat flux density, the parameters of the ceramics on the hot side should be input in the frame "Heat conductor" at the window of the intermediate thermal resistance calculation.

Power supply
       Our program carries out the calculation of the thermoelectric cooling system on the condition, that direct current is passing through the modules. Any other opportunities of the device supplying is not considered. At that the ripples of the direct current are supposed to be too small and thus omitted.

       The discrepancy value between the calculation by our program and the characteristics of real thermoelectric system can  amount to 20%. It is the usual value of error of the heat regimes calculations of many systems.  This error is defined not only with the inexactness of the thermal model, but also with the absence of the  possibility to consider  all construction peculiarities of the cooling system. It is impossible to define also exact values of thermophysical properties and other parameters of the construction elements.

Back


Selecting of modules, connection scheme and
power source

       Our program allows to calculate cooling and thermostatting systems that use semiconductor thermoelectric modules produced by KRYOTHERM company. We do manufacture more than 150 types of the thermoelectric modules, thus with the help of this program you can easily have a look at the behavior of any module in the specified thermoelectric system construction. To choose the module one should apply "Select Module" button  and choose one of the bookmarks with the type of the modules - micro modules, standard, high effective, special and multistage modules.
       As soon as you have the chosen module it is necessary to define its number. For the usual thermoelectric systems (for example, cool boxes for cars) one or two modules will satisfy your task. If you want to use module with the not very big value of the maximum cooling capacity, or if the chamber of the box has considerable dimensions, we would advise you to install greater amount of the thermoelectric modules.
       In case you have chosen several modules, depending on their amount they can be connected in following ways: series, parallel, or series-parallel. The choice of the connection scheme does not influence the characteristics of the module, but can be crucial if you are oriented on the particular power source. Let's consider the situation when you system needs to use two thermoelectric modules ICE-71. Usually each of these modules is supplied by 12 Volts. If you have the power source of 12 Volts, you should use parallel connection, but if you use 24 Volts power source, series connection would be preferable.
       The program allows to input voltage or current of the power source. The parameters of the power source are inputed for the whole thermoelectric system (for all modules, connected by the defined scheme). Thermoelectric modules require direct current supplying. Ripples of the current are possible, but not more than 5-10 %. Otherwise, thermoelectric module characteristics as well as features of the whole system become worse.

Back


Insulation thermal resistance calculation

       For the effective thermoelectric system operating the important point is an application of the thermal insulation materials. Cooling object should to be surrounded by the thermal insulation layer of the appropriate thickness.
       We offer to calculate the thermal resistance of the specified insulation in case you chose the Natural or Forced cooling type at the thermoelectric system cold side. Insulation thermal resistance will define the temperature difference between the object and ambience at the defined cooling capacity of the thermoelectric modules. In case  Flow at the cold side is specified it is necessary  to use reliable thermal insulation. But the program does not take into account thermal leakage through the insulation for this type of cooling. We suppose the insulation thermal resistance to be considerable.
       To calculate insulation thermal resistance it is necessary to input the dimensions of your object (cooling chamber): length Li, width Wi, height Hi of the box shape object and diameter Di and height Hi for the cylinder shape object.
       The one should choose from the offered list particular insulation material and input the value of its thickness. For the domestic refrigerators from 10 to 40 liters the polyurethane foam insulation of 20-50 mm thickness is sufficient. If you need another material, you may enter  the thermal conductivity coefficient by yourself.
       Heat transfer from the ambience to the object is made not only through the layer of the insulation material. The heat also passes by means of  convection between the external thermoelectric system surface and the ambience. The corresponding heat emission coefficient can be defined in options, for the usual conditions it may be considered as 5-10 W/(m·m·K).
       The program will define  the insulation thermal resistance on the base of the specified parameters. Moreover, you will  have the data about the object volume (cooling chamber), summary volume, chamber and external surface areas.

Back


The hot side and the cold side parameters determination

       The thermoelectric module in the cooling system works like the thermal pump transferring the heat from the object to the ambience. Thermoelectric module is not only the heat absorber as the energy releases at its hot surface and it should be removed to the ambience with the help of the heat-exchanger.
       To determine the modules' characteristics in the thermoelectric system it is necessary to set the parameters of the cold side and hot side. The program allows to define the parameters of the sides for three types of the heat transfer: Natural  convection, Forced convection, Flow. To choose the type of the cooling one should press the corresponding bookmark.
       The parameters of the sides firstly mean the thermal resistances of the heat-exchangers. The thermal resistances of the sides Rh and Rc are calculated per one module and they are summed up from the intermediate thermal resistances (Rh2 or Rc2) and the heat-exchanger thermal   resistances per one module (Rh1 or Rc1). We offer you to input or calculate the intermediate thermal resistance. It takes into account the modules mounting peculiarities (through thermal grease and heat conductor). You also can input or calculate the thermal resistance of the heat-exchanger (heat sink). Knowing the number of the heat-exchangers and the quantity of the modules, the program calculates the thermal resistances Rh1 and Rc1.
       For the case of Flow cooling (liquid or gas flow) it is necessary to set additionally the flow rate and the flow temperature at the inlet, and also the properties of the flow (density and heat capacity coefficient). While setting the cold side flow the main aim of the thermoelectric system work is the cooling of the flow from the inlet temperature Tcf0 to the specified temperature at the outlet Tcf1. The degree of cooling is determined by the flow equivalent Wc (W/K).  It characterizes the quantity of the heat which should be removed from the flow in order to cool it down for 1 Celsius degree.

Back


Intermediate thermal resistance calculation

       In the thermoelectric systems the modules mounting to the heat-exchangers is usually carried out through the special material which reduces the contact thermal resistance. The contact heat-conducting paste (thermal grease) is mostly used as the material and it has the thermal conductivity coefficient about 0.8 W/(m·K).
       The thermal grease is applied evenly with the thin layer on the module and heat-exchanger surfaces. Before applying the paste is preferably to be warmed up. In this case it fills up all micro-roughnesses of the contacting surfaces.  On the paste layer with thickness about 100 micrometers  the temperature drop at the hot side can be 2-4 degrees and more. Therefore, it is necessary to apply the thermal grease very carefully and to use the heat-exchangers, which surfaces have a minimal roughness.
       The heat conductor can be placed between the heat-exchanger and the module. The necessity of its usage is caused by the construction of the thermoelectric system. The heat conductor is  made from aluminium or other metal and as a rule it is installed between the cold side of the thermoelectric module and the cold heat sink. At the cold side the heat flux density and the temperature drop are less  than at the hot side. The heat conductor height is determined basically by the thermal insulation thickness.
       The program allows to take into account the heat conductor and thermal grease in the thermoelectric system. You can calculate the thermal resistances of grease and heat conductor, which sum is the intermediate thermal resistance - Rh2 at the hot side and Rc2 at the cold side.

Back


Heat exchanger thermal resistance calculation

       The heat exchangers are used for heat transfer from the hot surface of the thermoelectric module to the ambience and from the object to the cold module surface. As a rule, heat exchangers are lamellar heat-sinks made from the aluminium or other metal with high thermal conductivity.
       The heat sink thermal resistance depends on its dimensions (length L, width L2, the fin height h, the base thickness h2), number of fins, the fin thickness th, thermal conductivity of the heat sink material and the heat emission coefficient.
        The heat emission coefficient is determined by the type of heat transfer (natural or forced convection) and by the properties of gas or liquid. We offer you to calculate the heat emission coefficient, in case when heat transfer is carried out by Forced convection, or when Flow cooling is set. If heat transfer is carried out by means of Natural convection, the heat emission coefficient for the air one should set in the range from 2 to 10 W/(m·m·K), and for the water - in the range from 200 to 600 W/(m·m·K).
       On the base of the initial data the program calculates the thermal resistance of heat-exchanger finned surface.
       In addition, it is necessary to take into account heat transfer from finned surface to thermoelectric modules through the heat sink base. Usually, the heat sink area exceeds the thermoelectric module area a few times, therefore there is a considerable temperature field irregularity along the heat sink base. The program allows to input the irregularity coefficient value. This coefficient shows how much does the temperature difference between the ambient and center part of heat sink finned surface (over module mounting point) differs from the average temperature difference between the ambient and the heat sink finned surface. The exact determination of the irregularity coefficient is very hard scientific problem which deviates from our program. However, as the first approach, this value can be set equal to 1.2. Its minimum value is 1, and the maximum one is determined by the relation of heat sinks and modules areas.
       Knowing the thermal resistance of the heat sink finned surface, the dimensions of the base  and temperature irregularity coefficient, one can determine  the heat sink base thermal resistance.
       The thermal resistances of the heat sink base and finned surface give in sum  the total resistance of the heat sink at the hot side or the cold one. This value will determine the effectiveness of the thermoelectric system operation in many aspects.

Back


Heat emission coefficient calculation

       The heat-exchanger thermal resistance depends much on the heat emission coefficient. We can calculate this value  for the case of heat transfer by means of Forced convection or for the case of Flow by any side.
       The heat emission coefficient depends on the flow rate and properties of  coolant - liquid or gas. It is also necessary to determine the forcer mounting variant. The forcer can be a fan (for air or other gases) or a pump (for liquids). While the forcer is mounted on the heat-exchanger top (for example, compact axial fan), the flow rate is divided in two parts.
       The coolant flow speed is determined by the liquid/gas flow rate and by the heat sink cross-section area. The hydraulic diameter value plays important role in the heat exchange and it is calculated according the fin height and the clearance between fins.
       The character of flow - laminar or turbulent - is determined by the dimensionless Reynolds number, which is given by:

Re = (Speed of flow)·(Characteristic dimension)/(Kinematic viscosity)

       The laminar regime of flow is available at the Reynolds numbers less 2000. At the laminar regime the liquid or gas flows by layers, without mixing. At increasing of Reynolds number the transitional and turbulent flow regimes are available. They are characterized by the intensive coolant mixing.
       The heat exchange intensity is determined by the  dimensionless Nusselt number and at the turbulent flow it depends on Reynolds and Prandtl numbers, but at the laminar one the heat exchange intensity is determined by the fin height and clearance between the fins.
       The Nusselt number allows to calculate the heat emission coefficient by the following formula:

Heat emission coefficient = Nu·(Thermal conductivity)/(Characteristic dimension)

       Besides the heat emission coefficient calculating, the program allows to evaluate the heat exchanger hydraulic resistance. This value is necessary for fan or pump selecting, which could provide the set rate of coolant flow.

Back


Ambient and object heat rejected

Ambient
       To carry out the calculations of any thermoelectric system it is necessary to input the ambient temperature. The normal ambient temperature is 20 Celsius degrees. You can set the other values and the negative ones as well. However, KRYOTHERM guarantees the reliable work of the thermoelectric modules manufactured by the standard technology if they have the temperature not less than minus 50 and not higher than plus 80 Celsius degrees.

Object heat rejected
       Rather often we have the necessity of cooling of the object, which has the heat rejected inside. The object heat can be of any nature - electronic scheme (through  which the current passes), electric bulb, biological object, vessel in which the exothermal reaction takes place, etc. To take  into account this object property we give you the opportunity to input the object heat rejected value (watts).
       If your cooling system does not have such objects, then one should set the value of the heat releases equal to nought.
       The program considers the heat rejected only when Natural or Forced cooling is set by the cold side. In case of Flow our program does not consider the heat releases. Such systems are rarely available.

Back


Thermoelectric system calculation results

Main result
       The main goal and result of the calculations is the object temperature Tob determination in the specific thermoelectric system. In case of Flow cooling the basic aim of the calculations is the temperature Tcf1 determination. This is the flow temperature at the outlet of thermoelectric system cold side.

Temperature field
       As the calculation results we give the temperature distribution in the cooling system. In the usual thermoelectric system the hottest temperature is the thermoelectric module hot surface temperature Th, the lowest temperature is the module cold surface temperature Tc.
       The temperature difference dT=Th-Tc, made by thermoelectric module, consists of following parts:
     1) temperature difference on the hot side Th-Ta,
     2) the object cooling comparing to the ambience Ta-Tob,
     3) temperature difference on the cold side Tob-Tc.

       The single-staged modules of KRYOTHERM company allow to obtain the temperature difference up to 76 K. However, because of  thermal load Qc the working temperature difference between the module's sides is less and it is equal to 50-60 K. In the usual thermoelectric devices the object cooling comparing to the ambience is about 20-30 K, the temperature difference on the hot side of cooling system is 15-25 K, the temperature difference on the cold side of cooling system is  10-15K.
       In case of Flow setting by the hot or cold sides we calculate the temperature of the flow at the outlet Thf1 or Tcf1 at the given inlet flow temperature (Thf0 or Tcf0). We suppose that the flow temperature change has the exponential character. The program allows to determine the average value of the flow temperature Thfa or Tcfa along  the heat exchanger length.

The power characteristics
       In addition to the temperature field, the program allows to calculate the energetic characteristics of the modules' work in the thermoelectric system. These characteristics are: current I (A), voltage U (V), electric power consumption W=I·U (Wt), cooling capacity  Qc (Wt) and thermal power that is released at the module's hot surface Qh=Qc+W (Wt).
       At wish, these characteristics can be shown per one  module or per the whole thermoelectric cooling system (per all modules).
       The important parameter of thermoelectric system operation is the coefficient of performance COP. It characterizes the economy of thermoelectric system operation and numerically it is equal to the cooling capacity (Wt) at the power consumption 1 Wt:

                                                        COP=Qc/W.

Back