The unsteady state overall heat transfer coefficient in a chemical heat pump reactor: the NH3–CoCl2 system

2004 ◽  
Vol 59 (19) ◽  
pp. 4023-4031 ◽  
Author(s):  
Zine Aidoun ◽  
Marten Ternan
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Heat Pump ◽  
Unsteady State ◽  
Chemical Heat ◽  
Chemical Heat Pump ◽  
Overall Heat Transfer Coefficient

Study of Circuit Number on the Evaporator in CO2 Heat Pump Water Heater

2011 ◽  
Vol 71-78 ◽  
pp. 2266-2270 ◽  
Author(s):  
Kang Liu ◽  
Jing Lv ◽  
Song Bo Zhang ◽  
Jie Yang
Keyword(s):  
Heat Transfer ◽  
Carbon Dioxide ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Heat Pump ◽  
Temperature Difference ◽  
Water Heater ◽  
Overall Heat Transfer Coefficient ◽  
Heat Pump Water Heater ◽  
Simulation Package

In the design of a carbon dioxide heat pump water heater evaporator, the effect of the circuit number on the evaporator is investigated numerically by EVAP-COND 3.0 version simulation package of American National Institute of Standards and Technology. It is found that as the circuit number increases the temperature difference between the air and the refrigerant increases, but it reduces the overall heat transfer coefficient. The evaporator capacity will rise firstly, and then drop with the circuit number and achieve the maximum in the optimum circuit number. Therefore, selecting the appropriate circuit number of the evaporator can significantly improve the efficiency and optimize the design.

Utilization of a Graphite Foam Radiator on a Natural Gas Engine-Driven Heat Pump

2002 ◽  
Author(s):  
R. D. Ott ◽  
A. Zaltash ◽  
J. W. Klett
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Heat Pump ◽  
Gas Engine ◽  
Natural Gas Engine ◽  
Overall Heat Transfer Coefficient ◽  
Bulk Thermal Conductivity ◽  
Graphite Foam

A natural gas engine-driven heat pump was outfitted with a graphite foam radiator to demonstrate its thermal efficiency and compare it with that of a conventional radiator. A sequence of tests was performed with the graphite foam radiator operating in series with the standard aluminum radiator. Most aluminum air-to-water radiators exhibit an overall heat transfer coefficient up to 100 W/(m2·K). Laboratory experiments have demonstrated that a graphite foam radiator can achieve an overall heat transfer coefficient up to an order of magnitude larger. The mesophase pitch derived graphite foam is a material that offers excellent thermal management capability. The foam has an accessible surface area of 4 m2/g and an open cell structure with graphitic ligaments aligned parallel to the cell walls, giving it an overall bulk thermal conductivity of up to 175 W/(m·K). The bulk thermal conductivity of aluminum is 180 W/(m·K). The density of the graphite foam is a fifth of that of aluminum and its thermal diffusivity is three times greater than aluminum. These properties allow the graphite foam to be utilized in radiator, or any other heat exchanger, designs that are more efficient than conventional radiators. A graphite foam radiator designed to reject a given amount of heat will be smaller in size, weigh less, require less cooling air, and be quicker at removing heat than a conventional aluminum radiator.

scholarly journals A numerical model and validation of phase change material integrated thermoelectric radiant cooling panel

2019 ◽  
Vol 111 ◽  
pp. 01001
Author(s):  
Hansol Lim ◽  
Hye-Jin Cho ◽  
Seong-Yong Cheon ◽  
Soo-Jin Lee ◽  
Jae-Weon Jeong
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Numerical Model ◽  
Surface Temperature ◽  
Phase Change ◽  
Transfer Coefficient ◽  
Phase Change Material ◽  
Overall Heat Transfer Coefficient ◽  
Radiant Cooling ◽  
Change Material

A phase change material based radiant cooling panel with thermoelectric module (PCM-TERCP) is proposed in this study. It consists of two aluminium panels, and phase change materials (PCMs) sandwiched between the two panels. Thermoelectric modules (TEMs) are attached to one of the aluminium panels, and heat sinks are attached to the top side of TEMs. PCM-TERCP is a thermal energy storage concept equipment, in which TEMs freeze the PCM during the night whose melting temperature is 16○C. Therefore, the radiant cooling panel can maintain a surface temperature of 16◦C without the operation of TEM during the day. Furthermore, it is necessary to design the PCM-TERCP in a way that it can maintain the panel surface temperature during the targeted operating time. Therefore, the numerical model was developed using finite difference method to evaluate the thermal behaviour of PCM-TERCP. Experiments were also conducted to validate the performance of the developed model. Using the developed model, the possible operation time was investigated to determine the overall heat transfer coefficient required between radiant cooling panel and TEM. Consequently, the results showed that a overall heat transfer coefficient of 394 W/m2K is required to maintain the surface temperature between 16○C to 18○C for a 3 hours operation.

The Effect of Baffles in Shell and Tube Heat Exchangers

2009 ◽  
Vol 62-64 ◽  
pp. 694-699 ◽  
Author(s):  
E. Akpabio ◽  
I.O. Oboh ◽  
E.O. Aluyor
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Heat Exchangers ◽  
Proper Position ◽  
Process Industries ◽  
Overall Heat Transfer Coefficient ◽  
Shell And Tube ◽  
Optimal Values ◽  
Side Flow

Shell and tube heat exchangers in their various construction modifications are probably the most widespread and commonly used basic heat exchanger configuration in the process industries. There are many modifications of the basic configuration which can be used to solve special problems. Baffles serve two functions: Most importantly, they support the tubes in the proper position during assembly and operation and prevent vibration of the tubes caused by flow-induced eddies, and secondly, they guide the shell-side flow back and forth across the tube field, increasing the velocity and the heat transfer coefficient. The objective of this paper is to find the baffle spacing at fixed baffle cut that will give us the optimal values for the overall heat transfer coefficient. To do this Microsoft Excel 2003 package was employed. The results obtained from previous studies showed that to obtain optimal values for the overall heat transfer coefficient for the shell and tube heat exchangers a baffle cut of 20 to 25 percent of the diameter is common and the maximum spacing depends on how much support the tubes need. This was used to validate the results obtained from this study.

Energy Efficient Hybrid Nanofluids for Tubular Cooling Applications

2014 ◽  
Vol 592-594 ◽  
pp. 922-926 ◽  
Author(s):  
Devasenan Madhesh ◽  
S. Kalaiselvam
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Volume Concentration ◽  
Thermal Characteristics ◽  
Hybrid Nanofluid ◽  
Tubular Heat Exchanger ◽  
Overall Heat Transfer Coefficient ◽  
Flow Through ◽  
Hybrid Nanofluids

Analysis of heat transfer behaviour of hybrid nanofluid (HyNF) flow through the tubular heat exchanger was experimentally investigated. In this analysis the effects of thermal characteristics of forced convection, Nusselt number, Peclet number, and overall heat transfer coefficient were investigated.The nanofluid was prepared by dispersing the copper-titania hybrid nanocomposite (HyNC) in the water. The experiments were performed for various nanoparticle volume concentrations addition in the base fluid from the range of 0.1% to 1.0%. The experimental results show that the overall heat transfer coefficient was found to increases maximum by 30.4%, up to 0.7% volume concentration of HyNC.

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