Effect of Operating Conditions on the Performance of Two-Bed Closed-Cycle Solid-Sorption Heat Pump Systems

1995 ◽  
Vol 117 (3) ◽  
pp. 181-186 ◽  
Author(s):  
W. Zheng ◽  
W. M. Worek ◽  
G. Nowakowski
Keyword(s):  
Ambient Temperature ◽  
System Performance ◽  
Cooling Capacity ◽  
Heat Pumps ◽  
Operating Conditions ◽  
Operating Parameters ◽  
Closed Cycle ◽  
Sorption Heat ◽  
Cycling Speed ◽  
Sorption Heat Pump

The effect of two operating parameters, the regeneration temperature and the ambient temperature, on the performance of two-bed, closed-cycle solid-sorption heat pumps is investigated. The results show that increasing the regeneration temperature can improve both the COP and cooling capacity, and the effect on cooling capacity is more significant than the COP. Increasing the regeneration temperature from 180°C to 260°C, the cooling capacity increases by 50 percent and the COP improves 20 percent. When the ambient temperature drops, the system performance increases significantly. When the ambient temperature decreases by 10°C from the design point of 35°C, the COP and cooling capacity increases by 50 percent and 40 percent, respectively. Also, the bed cycling speed should be increased to achieve the optimum system performance when the regeneration temperature is higher or the ambient temperature becomes lower.

Performance Analysis of a Silica Gel-Water Adsorption Cooler: Impact of Nanofluids on Cooler Performance and Size

2015 ◽  
Author(s):  
I. P. Koronaki ◽  
M. T. Nitsas ◽  
E. G. Papoutsis ◽  
V. D. Papaefthimiou
Keyword(s):  
Heat Transfer ◽  
Silica Gel ◽  
Cooling Capacity ◽  
Heat Pumps ◽  
Coefficient Of Performance ◽  
Theoretical Research ◽  
Adsorption Chiller ◽  
Heat Transfer Fluids ◽  
Thermally Driven ◽  
Sorption Heat

Thermally driven chillers also known as sorption heat pumps have drawn considerable attention in recent years. They can be divided into two main categories: absorption (liquid-vapor) and adsorption (solid-vapor) systems. Even though adsorption cycles have relatively lower coefficient of performance compared to absorption cycles, however they prevail in terms of heat source, electric consumption for moving parts, crystallization etc. In order to overcome the drawback of low COP and specific cooling capacity, nanofluids, i.e. mixtures of nanometer size particles well-dispersed in a base fluid, can be used as heat transfer fluids as recent experimental and theoretical research has proved that nanofluids can exhibit a significant increase on heat transfer. In this study a two bed, single-stage adsorption chiller which utilizes the silica gel-water pair as adsorbent-refrigerant is simulated. The cooling capacity and the COP of the chiller are calculated for various cycle times. The usage of nanofluids as heat transfer fluids in the chiller evaporator and condenser and their effect on chiller performance and size is investigated. It is proved that the presence of nanofluids at different volume concentrations will enhance the cooling capacity and the COP of the adsorption chiller and therefore will lead to smaller, in terms of size, heat exchangers.

Performance Investigation of Single Adsorption Refrigeration System Driven by Solar Heat Storage

2018 ◽  
Vol 26 (03) ◽  
pp. 1850025
Author(s):  
Hicham Boushaba ◽  
Abdelaziz Mimet
Keyword(s):  
System Performance ◽  
Heat Storage ◽  
Cooling Capacity ◽  
Operating Conditions ◽  
Coefficient Of Performance ◽  
Solar Irradiation ◽  
Cooling Power ◽  
Condensation Temperature ◽  
Adsorption Refrigeration ◽  
Solar Heat

The aim of this paper is to provide a global study of an adsorption refrigeration machine driven by solar heat storage and collected by parabolic trough collector. The system operates with ammonia (as refrigerant) and activated carbon (as adsorbent). A mathematical model interpreting the progression of the heat and the mass transfer at each element of the prototype has been developed. The solar irradiation and the real ambient temperature variations corresponding to a usual summer day in Tetouan (Morocco) are considered. The system performance is evaluated trough specific cooling power (SCP) as well as solar coefficient of performance (SCOP), which was estimated by a dynamic simulation cycle. The pressure, temperature and adsorbed mass profiles in the Adsorber have been calculated. The effects of significant design and operating parameters on the system performance have been investigated. The results show the capability of our system to realize an encouraging performance and to overcome the intermittence of the adsorption refrigeration machines. For a daily solar irradiation of 18[Formula: see text]MJ[Formula: see text]m[Formula: see text] and operating conditions of evaporation temperature [Formula: see text]C, condensation temperature [Formula: see text]C and generation temperature [Formula: see text]C, the results show that the process could achieve an SCP of 115[Formula: see text]W[Formula: see text]kg[Formula: see text] and it could produce a daily specific cooling capacity of 3310[Formula: see text]kJ[Formula: see text]kg[Formula: see text], whereas its SCOP could attain 0.141.

Effect of Design and Operating Parameters on the Performance of Two-Bed Sorption Heat Pump Systems

1995 ◽  
Vol 117 (1) ◽  
pp. 67-74 ◽  
Author(s):  
W. Zheng ◽  
W. M. Worek ◽  
G. Nowakowski
Keyword(s):  
Heat Exchanger ◽  
Heat Pump ◽  
Heat Transfer Fluid ◽  
Switching Frequency ◽  
Operating Parameters ◽  
Switching Speed ◽  
Pump System ◽  
Heat Pump System ◽  
Sorption Heat ◽  
Sorption Heat Pump

The effect of design and operating parameters on the performance of closed-cycle, two-bed sorption heat pump systems were investigated. The parameters studied in this paper included the effects of bed switching frequency (i.e., the switching speed), the sorbent bed NTU, the thermal resistance within the sorbent, the contact resistance between the sorbent and the tube wall of the heat transfer fluid, the fraction of inert mass within the sorbent bed heat exchanger, and the amount of fluid resident within the heat exchanger. The results show that the performance of a sorption heat pump system is extremely sensitive to the switching speed. In fact, the value of the switching speed that optimizes the COP is different from the value that optimizes the overall cooling capacity. Such a performance characteristic allows the design of multispeed sorbent bed heat pumps to be operated in such a way to follow the load while still maximizing the system COP. However, operation of the system at switching speeds away from the optimum values can cause a dramatic deterioration in system performance.

Effects of Adsorbent Conductivity and Permeability on the Performance of a Solid Sorption Heat Pump

1999 ◽  
Vol 121 (1) ◽  
pp. 51-59 ◽  
Author(s):  
M. W. Ellis ◽  
W. J. Wepfer
Keyword(s):  
Thermal Conductivity ◽  
Heat Pump ◽  
Thermal Wave ◽  
Adsorption Equilibrium ◽  
Heat Pumps ◽  
Vapor Flow ◽  
Heating And Cooling ◽  
Improved Performance ◽  
Sorption Heat ◽  
Sorption Heat Pump

Solid sorption heat pumps can improve the effectiveness with which energy resources are used for heating and cooling. These systems operate by alternately heating and cooling beds of adsorbent material to produce a flow of refrigerant. The research presented here evaluates the effects of adsorbent thermal conductivity and permeability on the performance of a thermal wave solid sorption heat pump. In order to evaluate these effects, a numerical model of the thermal wave heat pump is developed. This model incorporates not only the effects of the conductivity and permeability, but also the effects of the adsorption equilibrium properties, refrigerant properties, application parameters, operating parameters, and bed geometry. For a typical air conditioning application, the model is used to study the influence of conductivity and permeability on the COP for systems using ammonia as a refrigerant. The results indicate that for the geometry considered, increasing the thermal conductivity of the adsorbent to 1 W/m-K can improve the COP to approximately 0.75. Further increases in conductivity do not yield improved performance. Furthermore, the reduced permeability associated with high conductivity adsorbents can impair vapor flow and lead to decreased performance.

Performance optimization of two-bed closed-cycle solid-sorption heat pump systems

1995 ◽  
Vol 31 (1-2) ◽  
pp. 1-9 ◽  
Author(s):  
W. Zheng ◽  
W. M. Worek ◽  
G. Nowakowski
Keyword(s):  
Heat Pump ◽  
Performance Optimization ◽  
Closed Cycle ◽  
Sorption Heat ◽  
Sorption Heat Pump

Dynamic Analysis of a Closed-Cycle Solar Adsorption Refrigerator Using Two Adsorbent-Adsorbate Pairs

1991 ◽  
Vol 113 (2) ◽  
pp. 73-79 ◽  
Author(s):  
A. Hajji ◽  
W. M. Worek ◽  
Z. Lavan
Keyword(s):  
Dynamic Analysis ◽  
System Performance ◽  
Inert Material ◽  
Operating Parameters ◽  
Closed Cycle ◽  
Zeolite 13X ◽  
Thermal Capacitance ◽  
Matrix Porosity ◽  
Capacitance Matrix

A dynamic analysis of a closed-cycle, solar adsorption refrigerator is presented. The instantaneous and daily system performance are studied using two adsorbent-adsorbate pairs, Zeolite 13X-Water and Chabazite-Methanol. The effect of design and operating parameters, including inert material thermal capacitance, matrix porosity, and evaporator and condenser temperatures on the solar and cycle coefficients of performance are evaluated.

scholarly journals Investigation of the Environmentally-Friendly Refrigerant R152a for Air Conditioning Purposes

2018 ◽  
Vol 9 (1) ◽  
pp. 119 ◽  
Author(s):  
Evangelos Bellos ◽  
Christos Tzivanidis
Keyword(s):  
Heat Pump ◽  
High Performance ◽  
Environmentally Friendly ◽  
Cooling Capacity ◽  
Heat Pumps ◽  
Operating Conditions ◽  
Coefficient Of Performance ◽  
Cooling Systems ◽  
Detailed Model ◽  
Ambient Temperatures

Heat pumps are efficient and well-established technologies for providing the proper cooling load in the building sector. The objective of this work is the parametric investigation of a heat pump operating with the promising refrigerant R152a for different operating conditions. More specifically, the heat pump is studied for different ambient temperatures, different indoor temperatures and various compressor rotational speeds. The cooling capacity and the coefficient of performance (COP) are the most important parameters which calculated in every scenario. A detailed model is developed in Engineering Equations Solver (EES) and it is validated with literature data. According to the final results, the system can operate in nominal conditions with 5 kW cooling capacity and a COP equal to 6.46. It is found that the COP can be ranged from 4 to 12 and the cooling capacity, while the cooling capacity can reach up to 9 kW. Moreover, a regression equation about the performance of the system is suggested. The obtained results indicate that the use of the R152a leads to high performance and so it can be an environmentally friendly choice for the cooling systems.

Thermo-Fluid Mechanics of Fluid Injection and Refrigeration System Performance Improvement

2007 ◽  
Author(s):  
B. G. Shiva Prasad ◽  
Philip Moeller ◽  
John Sheridan
Keyword(s):  
Performance Improvement ◽  
System Performance ◽  
Cooling Capacity ◽  
Heat Pumps ◽  
Control Technique ◽  
Fluid Injection ◽  
Refrigeration System ◽  
Flow Process ◽  
Design And Optimization ◽  
Flowing Stream

Injecting a fluid into a flowing stream is a common and powerful flow control technique to improve the flow process or performance of downstream components and machinery. This paper presents an application of such a technique to scroll compressors for improving the cooling capacity and efficiency of refrigerators and other heat pumps. It provides some insights into the physics of fluid injection and suggests methods for maximizing the benefits. Further, it discusses the need for CFD in system design and optimization and illustrates its application.

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