To ensure the most effective response: Please provide a rough, dimensioned sketch of the application, indicating the anticipated physical configuration and thermoelectric module placement. Please print this form and fill in the blanks. Each need for a cascade Cascade Devices is unique, so too should be the device selected to fill the need. Melcor has developed a computer aided design A multistage thermoelectric device should be used only system to help select a device. The three parameters list- where a single stage device does not fill the need.
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A heat sink that is toosmall means that the desired cold side temperature may not be obtained. The cold side of the thermoelectric is the side that gets cold when DC poweris applied. This side may need to be colder than the desired temperature of thecooled object. This is especially true when the cold side is not in directcontact with the object, such as when cooling an enclosure.
The temperature difference across the thermoelectric T relates to Thand Tc according to Equation 3. Estimating Qc, the heat load in watts absorbed from the coldside is difficult, because all thermal loads in the design must be considered.
Among these thermal loads are: Active: I2R heat load from the electronic devices Any loadgenerated by a chemical reaction Passive: Radiation heat loss between two close objects with differenttemperatures Convection heat loss through the air, where the air has adifferent temperature than the object Insulation Losses ConductionLosses heat loss through leads, screws, etc. Transient Load time requiredto change the temperature of an object Powering the Thermoelectric All thermoelectrics are rated for Imax, Vmax, Qmax,and Tmax, at aspecific value of Th.
Operating at or near the maximum power isrelatively inefficient due to internal heating Joulian heat at high power. The input power to the thermoelectric determines the hot sidetemperature and cooling capability at a given load. As the thermoelectric operates, the current flowing through it has twoeffects: 1 the Peltier Effect cooling and 2 the Joulian Effect heating.
The Joulian Effect is proportional to the square of the current. Therefore, asthe current increases, the Joule heating dominates the Peltier cooling andcauses a loss in net cooling. This cut-off defines Imax for thethermoelectric.
For each device, Qmax is the maximum heat load that can beabsorbed by the cold side of the thermoelectric. The Tmaxvalue is the maximum temperature difference across the thermoelectric. These values of Qmax and Tmax are shownon the performance curve Figure 3 as the end points of the Imaxline.
An Example Suppose a designer has an application with an estimated heat load of 22watts, a forced convection type heat sink with a thermal resistance of 0. The cold side of the thermoelectric will be in direct contact with the object. The designer has a Melcor CP1. The specifications for theCP1. The parameter Tfollows directly from Th and Tc. Without knowing the power into the thermoelectric, an exact value of Thcannot be found. Performance Curve.
An introduction to thermoelectric coolers