Operational characteristics of thermoelectric refrigeration

Advancements in contemporary physics in the field of semiconductors now make it possible to effectively utilize thermoelectric phenomenon for cooling and environment heating. Refrigerator applications using thermoelectric cooling effect are being built and introduced into industrial and military engineering design. Calculations on semiconductor thermoelectric refrigeration systems are based on relationships derived from considering the basic thermoelectric couple to be in an isolated control volume. In this pseudo environment the cooling capacity and coefficient of performance are based on the assumption that junction temperatures of the thermoelements are independent of the current. Test results on semiconductor refrigeration systems indicate however that the C.O.P. characteristic with the absence of artificial restraints do not have extremal values. Such conclusions can only' be observed if an experiment is conducted in which the junction temperatures are controlled (constant). Conclusions which are obtained account only for internal energy processes occurring within the control volume. However in actual practice the cooling capability, performance level are functions of the applied current. The results available (within the thesis proper) indicate that there is a direct functional relation between the thermoelectric couple and the environment to be regulated. The object of the thesis is to present the various operational parameters that relate system performance to the environment in which the thermoelectric module is required to perform' and control. The mathematical coupling between the thermoelectric junctions and the environments are assumed to be represented by a order function. The technique of utilizing a parametric analysis model enables a comprehensive engineering effort to establish the mathematical tools for competitive evaluation. Four major subcomponents sharply influence the design/performance of thermcouples for modular assembly. The thermal and electrical material properties of the elements fall into the most fundamental category. Power supply and regulation control are in a second major category. Properties and technique of material construction and processing are a third consideration. Heat exchanger devices provide further requirements to be considered. The various problems to be encountered are considered and the inter-acting of the major components are indicated. The extent to which these conditions limit the design/performance and the determination of the most advantageous comprmise is essentially the task considered. Methods are developed to determine the quantative effects of parametric adjustment. The design problems considered result in the requirements for the solution of the heat transfer equation in which the boundary conditions are stated. The solution to this class of problem is offered by the application of numerical analysis. The technique for solution is by the method termed, "overrelaxation" thereby effectively increasing the convergence rate of the finite difference equations, Advances and more sophisticated methods of digital computer utilization resulted in a comprehensive mathematical tool being afforded to the design engineer