Performance Optimization for a Multielement Thermoelectric Refrigerator with Linear Phenomenological Heat Transfer Law

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Lingen Chen ◽  
Fankai Meng ◽  
Yanlin Ge ◽  
Huijun Feng
Keyword(s):  
Heat Transfer ◽  
Performance Optimization ◽  
Heat Exchangers ◽  
Thermal Conductance ◽  
Electrical Current ◽  
Coefficient Of Performance ◽  
Junction Temperature ◽  
Thomson Effect ◽  
Electrical Currents ◽  
Temperature Solution

AbstractA model of a multielement thermoelectric refrigerator with another linear heat transfer law, the linear phenomenological heat transfer law Q\propto \Delta (1/T), is established. The refrigerating capacity and coefficient of performance (COP) are analyzed and optimized. The junction temperature solution equations are derived. The optimum electrical currents and thermal conductance allocation are discussed. The influences of thermoelectric element quantity and refrigerating temperature difference on the optimum performances and optimum electrical currents are analyzed. The results show that different optimization objectives have different requirements for the distribution of electrical current and thermal conductance. The refrigeration capacity is not proportional to the number of thermoelectric elements. It is found that the refrigerating capacity can be achieved only when the number of thermoelectric elements is matched for fixed external heat exchangers. The input electrical current and the allocation of the thermal conductance between the two heat exchangers can be optimized synchronously to achieve maximum refrigerating capacity or maximum COP. Performance is compared with that with a Newtonian heat transfer law. The influences of the Thomson effect are also examined. Performance of the refrigerator with Newtonian heat transfer law is higher than that of the refrigerator with linear phenomenological heat transfer law. The Thomson effect can improve the performance of the refrigerator.

Performance Optimization of Compact Ceramic High Temperature Heat Exchangers

2007 ◽  
Author(s):  
Q. Y. Chen ◽  
M. Zeng ◽  
D. H. Zhang ◽  
Q. W. Wang
Keyword(s):  
Heat Transfer ◽  
High Temperature ◽  
Heat Exchanger ◽  
Performance Optimization ◽  
Heat Exchangers ◽  
Radiation Heat Transfer ◽  
Surface Radiation ◽  
Radiation Heat ◽  
High Temperature Side ◽  
Temperature Heat

In the present paper, the compact ceramic high temperature heat exchangers with parallel offset strip fins and inclined strip fins (inclined angle β = 0∼70°) are investigated with CFD method. The numerical simulations are carried out for high temperature (1500°C), without and with radiation heat transfer, and the periodic boundary is used in transverse direction. The fluid of high temperature side is the standard flue gas. The material of heat exchanger is SiC. NuS-G.R(with surface and gaseous radiation heat transfer) is averagely higher than NuNo.R (without radiation heat transfer) by 7% and fS-G.R is averagely higher than fNo.R by 5%. NuS-G.R(with surface and gaseous radiation heat transfer) is averagely higher than NuS.R (with only surface radiation heat transfer) by 0.8% and fS-G.R is averagely higher than fS.R by 3%. The thermal properties have significantly influence on the heat transfer and pressure drop characteristics, respectively. The heat transfer performance of the ceramic heat exchanger with inclined fins (β = 30°) is the best.

Optimal Performance of an Endoreversible Four-Heat-Reservoir Absorption Heat-Transformer

2004 ◽  
Vol 11 (02) ◽  
pp. 147-159 ◽  
Author(s):  
Xiaoyong Qin ◽  
Lingen Chen ◽  
Fengrui Sun ◽  
Chih Wu
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
Heat Transfer Surface ◽  
Coefficient Of Performance ◽  
Heat Reservoir ◽  
Cycle Model ◽  
Surface Areas ◽  
Heating Load ◽  
Temperature Levels ◽  
Heat Transformer

Based on an endoreversible absorption heat-transformer cycle model operating between four temperature levels with linear (Newtonian) heat transfer law, the fundamental optimal relation between the specific heating load and the coefficient of performance, the optimal temperatures of the working substance, and the optimal heat transfer surface areas of the four heat exchangers are derived by using finite-time thermodynamics. Moreover, the effects of the cycle parameters on the cycle characteristic are studied by numerical examples. The results obtained herein can provide some guidance for the optimal design of absorption heat-transformers.

Performance of Aluminum and Carbon Foams for Air Side Heat Transfer Augmentation

2010 ◽  
Vol 132 (12) ◽  
Author(s):  
Patrick T. Garrity ◽  
James F. Klausner ◽  
Renwei Mei
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
Aluminum Foam ◽  
Carbon Foam ◽  
Ambient Air ◽  
Total Heat ◽  
Coefficient Of Performance ◽  
Transfer Model ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients

The air side heat transfer performance of three aluminum foam samples and three modified carbon foam samples are examined for comparison with multilouvered fins often found in compact heat exchangers. The aluminum foam samples have a bulk density of 216 kg/m3 with pore sizes of 0.5, 1, and 2 mm. The modified carbon foam samples have bulk densities of 284, 317, and 400 kg/m3 and machined flow passages of 3.2 mm in diameter. The samples were placed in a forced convection arrangement using a foil heater as the heat source and ambient air as the sink. A constant heat flux of 9.77 kW/m2 is applied throughout the experiments with the mean air velocity ranging from 1 to 6 m/s as the control parameter. The steady volume-averaged momentum equation and a two-equation nonequilibrium heat transfer model are employed to extract the volumetric heat transfer coefficients. Pressure drop measurements are correlated with the Darcy–Forcheimer relation. Empirical heat transfer correlations for the aluminum and carbon foam samples are provided. Using a hypothetical heat exchanger considering only the thermal resistance between the ambient air and the outer tube wall, the air side performance for each sample is modeled based on the local heat transfer coefficients and friction factors obtained from experiments. The performance of each sample is evaluated based on a coefficient of performance (COP, defined as the ratio of the total heat removed to the electrical input of the blower), compactness factor (CF, defined as the total heat removed per unit volume), and power density (PD, defined as the total heat removed per unit mass). Results show the carbon foam samples provide significant improvement in CF but the COP and PD are considerably lower than that for comparable multilouvered fin heat exchangers.

Optimization of a Solar-Driven Absorption Refrigerator Operating between Four Temperature Levels

2011 ◽  
Vol 354-355 ◽  
pp. 773-778
Author(s):  
Yue Wu Huang ◽  
De Xing Sun
Keyword(s):  
Heat Exchangers ◽  
Solar Collector ◽  
Operating Temperature ◽  
Thermal Conductance ◽  
Optimal Performance ◽  
Coefficient Of Performance ◽  
Optimum Operating ◽  
Optimum Operating Temperature ◽  
Temperature Level ◽  
Absorption Refrigerator

The optimal performance of the solar-driven thermodynamics cycle system consisting of a solar collector and a four-temperature-level absorption refrigerator is investigated, based on the linear heat-loss model of a solar collector and the irreversible cycle model of a four-temperature-level absorption refrigerator. A fundamental optimum relation is derived, from which the optimum operating temperature of the solar collector, the maximum overall coefficient of performance and the corresponding coefficient of performance of the four-temperature-level refrigerator are determined. It is proven that the total thermal conductance of the heat exchangers must be divided optimally between the four heat exchangers. The effects of the cycle parameters on the optimum operating temperature of the solar collector and the performance of the system are discussed by detailed numerical examples. The results obtained can describe the optimal performance of solar-driven four-temperature-level refrigerator affected simultaneously by the internal and external irreversibilities.

Heat transfer effect on optimal performance of two-stage thermoelectric heat pumps

2007 ◽  
Vol 221 (12) ◽  
pp. 1635-1641 ◽  
Author(s):  
L Chen ◽  
J Li ◽  
F Sun
Keyword(s):  
Heat Transfer ◽  
Heat Pump ◽  
Analytical Formula ◽  
Electrical Current ◽  
Heat Pumps ◽  
Coefficient Of Performance ◽  
Two Stage ◽  
Thermo Electric ◽  
Heating Load ◽  
Thermoelectric Heat

A model of two-stage semiconductor thermoelectric heat pumps with external heat transfer and internal irreversibility is built. Performance of the heat pump with Newton's heat transfer law is analysed and optimized using the combination of finite-time thermodynamics and non-equilibrium thermodynamics. The analytical formula about heating load versus working electrical current, and the coefficient of performance (COP) versus working electrical current are derived. For the fixed total number of thermoelectric elements, the ratio of number of thermo-electric elements of top stage to the total number of thermoelectric elements is also optimized for maximizing the heating load and the COP of the thermoelectric heat pump. The effects of design factors on the performance are analysed.

Thermodynamic Analysis of TEG-TEC Device Including Influence of Thomson Effect

2018 ◽  
Vol 43 (1) ◽  
pp. 75-86 ◽  
Author(s):  
Yuanli Feng ◽  
Lingen Chen ◽  
Fankai Meng ◽  
Fengrui Sun
Keyword(s):  
Thermoelectric Generator ◽  
Cooling Capacity ◽  
Thermodynamic Theory ◽  
Optimal Performance ◽  
Coefficient Of Performance ◽  
Junction Temperature ◽  
Thermoelectric Cooler ◽  
Thomson Effect ◽  
Equilibrium Thermodynamic ◽  
Cold Junction

AbstractA thermodynamic model of a thermoelectric cooler driven by thermoelectric generator (TEG-TEC) device is established considering Thomson effect. The performance is analyzed and optimized using numerical calculation based on non-equilibrium thermodynamic theory. The influence characteristics of Thomson effect on the optimal performance and variable selection are investigated by comparing the condition with and without Thomson effect. The results show that Thomson effect degrades the performance of TEG-TEC device, it decreases the cooling capacity by 27 %, decreases the coefficient of performance (COP) by 19 %, decreases the maximum cooling temperature difference by 11 % when the ratio of thermoelectric elements number is 0.6, the cold junction temperature of thermoelectric cooler (TEC) is 285 K and the hot junction temperature of thermoelectric generator (TEG) is 450 K. Thomson effect degrades the optimal performance of TEG-TEC device, it decreases the maximum cooling capacity by 28 % and decreases the maximum COP by 28 % under the same junction temperatures. Thomson effect narrows the optimal variable range and optimal working range. In the design of the devices, limited-number thermoelectric elements should be more allocated appropriately to TEG when consider Thomson effect. The results may provide some guidelines for the design of TEG-TEC devices.

Thermoeconomic Analysis on the Performance Characteristics of a Multi-Stage Irreversible Combined Heat Pump System

2000 ◽  
Vol 122 (4) ◽  
pp. 212-216 ◽  
Author(s):  
Jincan Chen ◽  
Chih Wu
Keyword(s):  
Heat Transfer ◽  
Heat Pump ◽  
Heat Exchangers ◽  
Power Input ◽  
Coefficient Of Performance ◽  
Working Fluid ◽  
Pump System ◽  
Heat Pump System ◽  
Maximum Profit ◽  
Multi Stage

A cycle model of a multi-stage combined heat pump system, which includes the irreversibility of finite rate heat transfer across finite temperature differences and the irreversibilities inside the working fluid, is established and used to investigate the influence of these irreversibilities on the performance of the system. The profit of operating the heat pump system is taken as an objective function for optimization. The maximum profit is calculated for a given total heat transfer area or total thermal conductance of heat exchangers. The coefficient of performance, heating load, and power input at the maximum profit are determined. The distribution of the heat transfer areas or the thermal conductances of heat exchangers and the temperature ratios of the working fluids of two adjacent cycles in heat exchange processes are optimized. The results obtained here are generally significant. They are suitable for an arbitrary-stage irreversible and endo- reversible combined heat pump system. [S0195-0738(00)01104-3]

Efficiency Optimizations of an Irreversible Brayton Heat Engine

1998 ◽  
Vol 120 (2) ◽  
pp. 143-148 ◽  
Author(s):  
C.-Y. Cheng ◽  
C.-K. Chen
Keyword(s):  
Heat Transfer ◽  
Thermal Efficiency ◽  
Heat Exchangers ◽  
Heat Engine ◽  
Thermal Conductance ◽  
Working Fluid ◽  
Reservoir Temperature ◽  
Temperature Ratio ◽  
Conductance Ratio ◽  
Internal Irreversibility

A steady-flow approach for finite-time thermodynamics is used to calculate the maximum thermal efficiency, its corresponding power output, adiabatic temperature ratio, and thermal-conductance ratio of heat transfer equipment of a closed Brayton heat engine. The physical model considers three types of irreversibilities: finite thermal conductance between the working fluid and the reservoirs, heat leaks between the reservoirs, and internal irreversibility inside the closed Brayton heat engine. The effects of heat leaks, hot-cold reservoir temperature ratios, turbine and compressor isentropic efficiencies, and total conductances of heat exchangers on the maximum thermal efficiency and its corresponding parameters are studied. The optimum conductance ratio could be found to effectively use the heat transfer equipment, and this ratio is increased as the component efficiencies and total conductances of heat exchangers are increased, and always less than or equal to 0.5.

EXPERIMENTAL STUDY ON HEAT TRANSFER AND PRESSURE DROP CHARACTERISTICS FOR WELDED EMBOSSING TYPE PLATE HEAT EXCHANGERS

2011 ◽  
Vol 19 (02) ◽  
pp. 113-120 ◽  
Author(s):  
JONG YUN JEONG ◽  
CHUNG WOO JUNG ◽  
SANG-CHUL NAM ◽  
YONG TAE KANG
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Reynolds Number ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Heat Exchangers ◽  
Plate Heat Exchanger ◽  
Plate Heat ◽  
Temperature Solution ◽  
Fanning Friction Factor

Heat transfer and pressure drop characteristics of the welded plate heat exchangers are experimented to apply the high- and low-temperature solution heat exchanger (SHX) of absorption systems. Two different SHXs were made using the seam and tig welding method. In this paper, the welded embossing type plate heat exchangers were tested by controlling mass flow rate and inlet/outlet temperatures. It was found that heat transfer and pressure drop performance increased with increasing Reynolds number. It was also found that the pressure drop from the present W-embossing type plate heat exchanger was much lower than that from the brazed type, as low as 1/7 times. The experimental correlations for Nusselt number and Fanning friction factor were developed with the error bands of ± 20% and ± 25%, respectively. These results provide a guideline to apply the welded plate heat exchanger for the solution heat exchanger of absorption systems.

Experimental and theoretical investigation of small-scale cooling system equipped with helically coiled evaporator and condenser

2011 ◽  
Vol 226 (3) ◽  
pp. 724-737 ◽  
Author(s):  
A Elsayed ◽  
R K Al-dadah ◽  
S Mahmoud ◽  
A Rezk
Keyword(s):  
Heat Transfer ◽  
Performance Optimization ◽  
Cooling System ◽  
Coefficient Of Performance ◽  
Small Scale ◽  
Geometrical Parameters ◽  
Helical Coil ◽  
Straight Tube ◽  
Performance Study ◽  
Coil Diameter

Utilizing helically coiled tubes evaporator and condenser in cooling applications is promising due to their higher heat transfer coefficients compared to straight tube because of the effect of centripetal forces. With growing interest in miniature and efficient refrigeration systems, small helical coil diameter can offer significant advantages in terms of being compact, lightweight, and improved coefficient of performance (COP). This article describes a performance study of small-scale vapour compression cooling system (100 W cooling capacity) equipped with shell and helically coiled tube evaporator and condenser. A detailed mathematical model has been developed for this system based on thermodynamic principles and relevant heat transfer correlations. The model was validated using experimental results from a representative small size cooling system with agreement of ±5 per cent. The model was then used to carry out performance optimization in terms of the evaporator and condenser geometric parameters including helical coil diameter, tube inside diameter, and surface area ratio. For the range of geometrical parameters investigated, the model predicts that as the coil diameter decreases, the Cooling COP improves.

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