Performance Curves for Single-Stage Vapor Compression Cycles With Solution Circuit

1991 ◽  
Vol 113 (2) ◽  
pp. 221-227 ◽  
Author(s):  
K. Amrane ◽  
M. V. Rane ◽  
R. Radermacher
Keyword(s):  
Weak Solution ◽  
High Temperature ◽  
Heat Pump ◽  
Solution Concentration ◽  
Operating Conditions ◽  
Single Stage ◽  
Solution Temperature ◽  
Ammonia Vapor ◽  
Vapor Compression ◽  
Performance Curves

The performance curves for a single-stage vapor compression heat pump with solution circuit (VCHSC) and for its modified version, the cycle using a subcooler and a preheater, are obtained and are compared for the same total UA value including all heat exchangers. The two cycles are simulated at low and high temperature lifts. The weak solution concentration and flow rate are varied. The parameters studied are the cooling COP, the solution heat exchanger (SHX) effectiveness, the pressure ratio, the solution temperature glides in the absorber and the desorber, the desorber load, and the distribution of the UA value. Changing the weak solution concentration from 20 to 90 wt% ammonia increased the desorber load ten times. The cooling COP improved by as much as 20 percent by incorporating the preheater and the subcooler, for both the low and the high temperature lifts. Compared to the conventional ammonia vapor compression cycle, the modified VCHSC showed a maximum improvement in cooling COP of 88 and 35 percent for the low and high temperature lifts, respectively. The results indicate that VCHSC is a very versatile heat pump and/or refrigeration system suitable for a wide range of applications and changing operating conditions.

Second-Law Analysis of Vapor Compression Heat Pumps With Solution Circuit

1994 ◽  
Vol 116 (3) ◽  
pp. 453-461
Author(s):  
K. Amrane ◽  
R. Radermacher
Keyword(s):  
Heat Pump ◽  
Heat Pumps ◽  
Single Stage ◽  
Heat Transfer Fluid ◽  
Second Law ◽  
Fluid Temperature ◽  
Ammonia Vapor ◽  
Vapor Compression ◽  
Second Law Analysis ◽  
Work Input

A second-law analysis is conducted on both the single-stage vapor compression heat pump with solution circuit (VCHSC) and its modified version, the cycle with a preheater and additional desorber. The results are compared to a conventional heat pump cycle operating with pure ammonia. The location and magnitude of the irreversibilities of the individual components constituting the cycles are determined. The entropic average temperature is used in computing the irreversibilities. The total work input to the heat pumps is then conveniently decomposed into two parts: the minimum work input or the work of a reversible cycle operating between the desorber and absorber entropic average temperatures, plus an additional input of work caused by the irreversibilities of the different processes of the cycles. The analysis reveals that the compressor is the most inefficient component of the heat pumps with losses accounting for about one fourth of the work input. The irreversibilities in the desorber and absorber are found to be minimum when there is a good match in both the solution and heat transfer fluid temperature glides. By adding a preheater and an additional desorber, the irreversibilities in the single-stage VCHSC are considerably reduced. However, it is shown that it is the preheater and not the additional desorber that has by far the most significant impact on the heat pump’s efficiency improvements. Compared to a conventional ammonia vapor compression cycle, the modified VCHSC, which has twice as many sources of irreversibility, shows nevertheless a maximum improvement of 56.1 percent in second-law efficiency.

Performance of a Constrained Microscale Film Bubble Absorber Under System Operating Conditions

2008 ◽  
Author(s):  
Ruander Cardenas ◽  
Jeromy Jenks ◽  
Myeong Chan Jo ◽  
Vinod Narayanan
Keyword(s):  
Weak Solution ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Operating Conditions ◽  
Solution Temperature ◽  
Inlet Temperature ◽  
Vapor Flow ◽  
Ammonia Vapor ◽  
Vapor Bubbles

Absorption of ammonia vapor bubbles into a constrained thin film of ammonia-water solution is presented in the context of potential reduction in size of a heat-actuated heat pump component. A large-aspect-ratio channel with a depth of 600 μm restricts the thickness of the weak solution film, while ammonia vapor bubbles are injected from a porous wall. Experiments are performed at a nominal system pressure of 6.2 bar absolute and at an inlet weak solution temperature of 75 °C. A counter flowing coolant at a fixed inlet temperature of 58 °C removes the generated heat of absorption. The mass flow rate of the weak solution, vapor flow rate, and mass flow rate of the coolant solution are varied. Results indicate that a desirable operating condition for the absorber considering both heat and mass transfer attributes is obtained for a flow rate of 1.5 g/min of vapor and 35 g/min of weak solution. Variation of the coolant flow rate does not significantly affect the overall heat transfer coefficient at a low vapor flow rate of 1 g/min. Under these operating conditions, preliminary geometric scaling estimates indicate that a 11.3 kW heat load absorber would require a heat exchange surface area of 0.88 m2. The excess pressure drop penalty on the vapor side across the porous plate for this absorber needs to be considered in terms of the overall absorption cycle performance.

scholarly journals Environmental tests of vapor compression heat pump for space applications

2020 ◽  
pp. 240-240
Author(s):  
Xudong Ma ◽  
Rui Ma ◽  
Yilin Ye ◽  
Suying Yan ◽  
Feng Wang ◽  
...  
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Heat Pump ◽  
Low Temperatures ◽  
Heat Pumps ◽  
Coefficient Of Performance ◽  
Vapor Compression ◽  
Space Applications ◽  
Suitable Temperature ◽  
High And Low Temperatures

Heat pumps are needed to provide a suitable temperature for both people and equipment in spacecraft. This paper reports on work designed to see if vapor compression heat pumps, in particular, can be expected to function normally in space. A vapor compression heat pump was built and tested under conditions of high temperature (70?C), low temperature (0?C), and near-vacuum (10-4 Pa). It was found that the coefficient of performance of this heat pump was 2.99 at both high and low temperatures, and was 2.1 under near vacuum conditions. The results suggest that vapor compression heat pumps are suitable for use in space.

Performance Evaluations of LiCl and LiBr for Absorber Design Applications in the Open-Cycle Absorption Refrigeration System

1997 ◽  
Vol 119 (2) ◽  
pp. 165-173 ◽  
Author(s):  
K. J. Kim ◽  
T. A. Ameel ◽  
B. D. Wood
Keyword(s):  
Chemical Potential ◽  
Mass Transfer Rate ◽  
Cooling Water ◽  
Solution Concentration ◽  
Operating Conditions ◽  
Solution Temperature ◽  
Solution Flow Rate ◽  
Absorption Refrigeration ◽  
Solution Flow ◽  
Open Cycle

Both LiCl and LiBr solutions were considered for potential use in a solar-driven Open-Cycle Absorption Refrigeration (OCAR) system. A vertical falling film absorber was proposed and built to evaluate the performance of LiCl and LiBr as an absorbent. Absorption experiments were performed and the results are reported for typical operating conditions of nonabsorbable concentrations, solution concentration, solution temperature, cooling water temperature, absorber pressure, and solution flow rate, in terms of mass transfer rate. In general, LiBr outperformed LiCl in terms of effective absorption rate. Based upon experimental results, the required absorber area was estimated for both LiCl and LiBr. The small chemical potential of LiCl relative to LiBr leads to a larger absorber area. The cost for the required solution storage for three-ton cooling capacity of the present OCAR system was found to be high for both LiCl and LiBr. The pumping cost was estimated to be less than 0.1 kW for both.

Performance of a single-stage recuperative high-temperature air source heat pump

2021 ◽  
Vol 193 ◽  
pp. 116969
Author(s):  
Shoujun Sun ◽  
Hao Guo ◽  
Ding Lu ◽  
Yin Bai ◽  
Maoqiong Gong
Keyword(s):  
High Temperature ◽  
Heat Pump ◽  
Single Stage ◽  
Air Source Heat Pump

scholarly journals A Novel Ground-Source Heat Pump with R744 and R1234ze as Refrigerants

Energies ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 5654
Author(s):  
Giuseppe Emmi ◽  
Sara Bordignon ◽  
Laura Carnieletto ◽  
Michele De Carli ◽  
Fabio Poletto ◽  
...  
Keyword(s):  
High Temperature ◽  
Heat Pump ◽  
High Temperatures ◽  
Real Data ◽  
Energy Performance ◽  
Operating Conditions ◽  
Two Stage ◽  
Carrier Fluid ◽  
Ground Source ◽  
Novel Concept

The energy-saving potential of heat pump technology is widely recognized in the building sector. In retrofit applications, especially in old and historic buildings, it may be difficult to replace the existing distribution and high-temperature emission systems. Often, historical buildings, especially the listed ones, cannot be thermally insulated; this leads to high temperatures of the heat carrier fluid for heating. In these cases, the main limits are related, on the one hand, to the reaching of the required temperatures, and on the other hand, to the obtaining of good performance even at high temperatures. To address these problems, a suitable solution can be a two-stage heat pump. In this work, a novel concept of a two-stage heat pump is proposed, based on a transcritical cycle that uses the natural fluid R744 (carbon dioxide) with an ejector system. The second refrigerant present in the heat pump and used for the high-temperature stage is the R1234ze, which is an HFO (hydrofluoro-olefin) fluid. This work aims to present the effective energy performance based on real data obtained in operating conditions in a monitoring campaign. The heat pump prototype used in this application is part of the H2020 Cheap-GSHP project, which was concluded in 2019.

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