Performance Of Thermoelectric Heat Pump Research Articles

Performance optimisation of two-stage exoreversible thermoelectric heat pump in electrically series, parallel and isolated configurations

A configuration of the behaviour of an exoreversible two-stage semiconductor thermoelectric heat pump (TEHP) in three different modes, i.e., electrically series, electrically parallel and electrically separated is devised. The TEHP performance assuming Newton's heat transfer law is evaluated through a combination of finite time thermodynamics (FTT) and non-equilibrium thermodynamics. A formulation based on the heating load versus working electrical current and coefficient of performance (COP) versus working electrical current is applied in this study. For fixed total number of thermoelectric elements, optimisation of number of thermoelectric elements of the top stage for maximising the heating load and COP is done here. The complete analysis of effects of various design parameters on the performance of TEHP is formulated. Three thermodynamic models for multi-stage TEHP system considering internal irreversibilities are developed in the matrix laboratory Simulink environment. For typical operating conditions of TEHP system with total 30 thermocouples, the maximum value of COP is improved from 4.56 to 5.20 for same current in electrically parallel mode. This analysis will be helpful in designing the actual multistage TEHPs.

Optimal sizing of a thermoelectric heat pump (THP) for heating energy-efficient buildings

This paper aims to determine the optimal design and operating conditions of an air-to-air thermoelectric heat pump (THP) composed of thermoelectric modules (TEMs) and two heat sinks, coupled to an energy-efficient building. We focus on the optimal number of TEMs and the optimal electrical current for three standard cases. The performance is quantified using two different coefficients of performance (COP) definitions: performance of THP only (COPHP) and performance of THP coupled to an energy-efficient building (COPu). These COP are also studied for both instantaneous and seasonal conditions. We show that for each coupling, a range of modules exists, with which the maximum performance of the THP can be approached, by simply adapting the electrical current for each condition. Finally, the seasonal performance COPHPs/COPus for the French city of Macon is estimated and compared for the three cases considered. The original sizing approach proposed here leads to a slight increase of the COPHPs/COPus (up to +4%), compared to the classical design based on instantaneous nominal conditions (norm). Moreover, we show that the optimal number of modules can be largely reduced (up to −39% for the cases considered) compare with nominal condition method.

Effects of heat reservoir temperatures on the performance of thermoelectric heat pump driven by thermoelectric generator

On the basis of the model of the thermoelectric heat pump driven by thermoelectric generator device with external heat transfer, this paper analyzes the effects of generator heat source temperature and heat pump heating temperature on the optimal performance and optimal variables of the combined system for typical thermoelectric element properties using the combination of finite time thermodynamics and non-equilibrium thermodynamics by detailed numerical examples. For fixed total number of thermoelectric elements and fixed total thermal conductance of heat exchangers, the allocations of thermoelectric elements between the thermoelectric generator and the thermoelectric heat pump, and thermal conductance among the four heat exchangers, are optimized for maximum heating load and coefficient of performance (COP), respectively. The change features of optimal design variables are obtained. The results of numerical simulation show that optimization is necessary and effective. By optimization, the heating load, COP and extreme heating temperature are improved. When the thermoelectric generator and the thermoelectric heat pump work at a difference of 150 and 20 K, respectively, a COP of ∼0.15 could be reached that is considerable for application in a wide scale for specific purposes. The maximum heating load and maximum COP of the irreversible model and exo-reversible model are compared. The difference between the two models show the effects of external heat transfer irreversibilities on the performance of the combined device.

Effect of Heat Transfer on the Performance of Thermoelectric Heat Pumps

AbstractThe performance analysis of thermoelectric (semiconductor) heat pumps is performedusing the combined method of finite time thermodynamics and non-equilibriumthermodynamics. The heating load and coefficient of performance (COP) expressionsfor the heat pump, which is composed of multi-elements, are derived with con-siderations of heat transfer irreversibility in the heat exchangers between the heatpump and the external heat reservoirs as well as the other internal irreversibilities.Numerical examples are provided. The effects of heat transfer, the number of elementsand the other design parameters on the performance of the heat pump are analyzed.IntroductionSeveral authors have applied the combined method of finite time thermodynamics orentropy generation minimization [1–6] and non-equilibrium thermodynamics [7–9] tothe analysis of thermoelectric (semiconductor) heat pump [10–13]. They analyzed theeffect of finite-rate heat transfer between the thermoelectric device and its externalreservoirs on the performance of the single-element thermoelectric heat pump. Inpractice, a thermoelectric heat pump is composed of many fundamental thermoelectricelements. It is a multi-element device. In the present paper we will investigate thecharacteristics of multi-element thermoelectric heat pumps related to the irreversi-bilities of finite-rate heat transfer, Joulean heat inside the thermoelectric device, andthe heat leak through the thermoelectric couple leg. The expressions for the heatingload and the coefficient of performance (COP) of the multi-element thermoelectricheat pump are derived. The effects of various design parameters on the performance ofthe heat pump are analyzed.

98/04172 Use of multi-stage cascades to improve performance of thermoelectric heat pumps

98/04172 Use of multi-stage cascades to improve performance of thermoelectric heat pumps

Use of multi-stage cascades to improve performance of thermoelectric heat pumps

A thermoelectric heat pump is a miniature solid state device used to pump small amounts of heat. Potential uses range from the cooling of electronic components to dorm size refrigerators. An ongoing study at the U.S. Naval Academy proposes to use a miniature thermoelectric heat pump to maintain a neutron dosimeter at near constant temperatures in order to obtain more accurate readings. Unfortunately, the coefficient of performance of the heat pump decreases rapidly with increasing temperature difference. The current study investigates the potential improvement in heat pump performance that can be obtained by cascading two or more heat pumps in series operation.

The maximum coefficient of performance of thermoelectric heat pumps

SYNOPSIS The effect of three main irreversibilities existing in thermoelectric devices on the performance of a thermoelectric heat pump is investigated. The coefficient of performance and the heating load of the heat pump are derived. The optimal performance of the heat pump at maximum coefficient of performance is discussed, and the rational working region of the heat pump is determined. The optimal structure of the device is also described. The results obtained here are more realistic than those derived from nonequilibrium thermodynamics.

Entropy Production and Thermoelectric Device Performance

Integral forms for the thermal efficiency of thermoelectric generators, the coefficient of performance of thermoelectric refrigerators, and the coefficient of performance of thermoelectric heat pumps are derived. These forms are obtained for the isotropic material, nonsteady-state, nonadiabatic leg surface case. An example of the use of these forms is given.

The influence of the Thomson coefficient and variable resistivity on thermoelectric heat pump performance

Steady-state, closed form equations are presented for the temperature distribution, heat removal and coefficient of performance of a single stage, thermoelectric heat pump. The Seebeck coefficient is expressed as a logarithmic function of temperature. This expression permits the performance of elements made of thermoelectric materials with the same average Seebeck coefficient but with different values of Thomson coefficient to be compared. An expression for electrical resistivity as a linear function of temperature is also introduced. Thus, the performance of thermoelectric heat pumps made of materials having the same average resistivity but resistivities that are different linear functions of temperature can be compared. The results show that for positive Thomson coefficients, the Thomson effect increases both the rate of heat removal and the coefficient of performance. Negative Thomson coefficients have the opposite effect. For thermoelectric materials used in heat pumping applications, the electrical resistivity increases with temperature. This variation generally has less influence on performance than the Thomson effect. A numerical example is given which demonstrates that serious analytical errors can result by neglecting the influence of the Thomson effect and variable resistivity when calculating the performance of a thermoelectric heat pump.

Influence of spatially dependent properties on the performance of a thermoelectric heat pump

A study is presented of the performance of thermoelectric heat pumps with spatially dependent properties. The Seebeck coefficient, electrical resistivity and thermal conductivity are assumed to vary linearly with position. The performance criteria of interest include maximum no-load temperature difference, maximum coefficient of performance, maximum heat pumping capacity, coefficient of performance under conditions giving maximum heat pumping capacity and heat pumping capacity under conditions giving maximum coefficient of performance. Throughout the investigation it is assumed that the longitudinal surface of the thermoelement is insulated and that the fin conductances at the hot and cold junctions are infinite. The effect of spatial dependence of each property on the performance criterion is analyzed individually and then in physically appropriate combinations. It is shown that certain small linear variations in the Seebeck coefficient and the electrical resistivity act to increase all the performance criteria. However, small linear variations in the thermal conductivity decrease the performance criteria. In addition, it is shown that the spatial dependence of the thermal conductivity is not nearly as important as the dependence of the electrical resistivity and the Seebeck coefficient. Therefore, a net increase in the performance criteria should be possible through the use of controlled spatial property dependence.