Performance of a Residential-Sized GAX Absorption Chiller

Abstract

This research effort involved experimentally testing an advanced-cycle, ammonia-water absorption chiller with a cooling capacity of 17.6 kW (5 refrigeration tons (RT)). The system was a generator-absorber heat exchange (GAX) cycle and was sized for residential and light commercial use, where very little absorption equipment is currently used. The components of the cycle were assembled with instrumentation, including flow meters, pressure transducers, and thermocouples. The findings of the research were cycle cooling load and coefficient of performance (COP), as well as many component heat duties and working fluid state points throughout the cycle. The COP of the chiller at essentially full load was measured at 0.68. A simulation of the GAX cycle was performed with a computer program that predicted the heat duties of each component and the cooling load of the cycle. The simulation of the GAX cycle and experimental testing compared closely. Existing market research shows that significant business opportunities exist for a GAX heat pump or chiller with a cooling COP of 0.70 or greater. The work performed in this study consisted of testing a GAX cycle with a COP that approached the target value of 0.70 and identified improvements that must be made to reach the target COP value.

Theoretical and experimental evaluation of an indirect-fired GAX cycle cooling system

“…The GAX cycle is a system that provides the highest coefficient of performance of any single effect absorption cycle. Theoretical studies report for GAX systems COP th 30% higher than single effect cycles [4,5]; recently some experimental studies of GAX cycle for air-conditioning and refrigeration have been reported [6,7]. The GAX technology was theoretically developed by Altenkirch in 1913 [4], but the first prototype working with natural gas was constructed in 1980.…”

Energy modelling and field testing of natural gas absorption heat pump system in cold climate - Canada

“…A research group in Ohio (Priedeman & Garrabrant, 2001) experimentally tested the performance of a residential sized gas-fired absorption chiller with GAX. The capacity of the tested heat pump was 17.5 kW (5 refrigeration tons).…”

“…A recommendation that is common among absorption heat pump systems, including gas-fired systems, is the incorporation of a GAX in the cycle (Kang et al, 2000;Garimella et al, 2016;Phillips, 1990;Velázquez & Best, 2002). The GAX cycles have consistently shown to boost the COP values and offer energy and cost saving potential (Priedeman & Garrabrant, 2001;Velázquez & Best, 2002;Engler et al, 1997). However, a GAX cycle alone will not maximize the potential of the GAHP system, reduction of part load and maximizing time that the GAHP operates at full load is crucial in preventing unnecessary losses that reduce the efficiency of the overall system (Velázquez & Best, 2002).…”

“…To have a period of GAHP operation to be considered steady state, the system is required to run for a minimum of 30 minutes, as stated in other GAHP studies (Priedeman & Garrabrant, 2001). Due to the oversizing of the GAHP for the house, dump loads were required to meet this load.…”

Experimental studies on air-cooled NH3–H2O based modified gax absorption cooling system

“…Apart from the influence of the sink temperature on the system performance, they also analyzed the influence of other parameters such as the flow rate in the GAX heat transfer loop. Priedeman et al (2001) developed a 17.5 kW GAX system which employs NH 3 eH 2 0 as the working fluid and natural gas as the heat source. The system was tested at an ambient temperature of 35 C. The system attained a COP of 0.68 under a full load condition.…”