Improving Refrigeration Cycle Efficiency by Evaporative Precooling the Condenser Inlet Air
Abstract
The need to improve the energy performance of Heating, Ventilation & Air Conditioning (HVAC) units has always been a primary goal for designers as they implement new concepts and/or modifications to the standard vapor compression cycle. Recently, this primary goal has taken on an added importance due to the phasing out of conventional refrigerants that harm the environment. The newer environmentally safe refrigerants that are being considered as replacements have been shown to hinder the performance of HVAC units. A new method to increase the performance of HVAC units is investigated herein with the approach based on the integration of evaporative precooling to the air side of an HVAC system’s condenser.
The goal of this project is two-fold, namely to develop a facility and methodology to test the performance of HVAC units with precooling applied to the HVAC unit’s condenser, and then to perform and evaluate the results of testing. The psychometric testing facility at Texas A&M was restored to operation in accordance with AHRI 210/240 standard and then modified in order to accommodate the addition of an evaporative cooler. The testing facility allowed for the complete control of temperature and relative humidity of two separate rooms in order to simulate indoor and outdoor conditions.
The efficiencies of the HVAC unit were shown to improve with the implementation of evaporative precooling. The improvement of the coefficient of performance (COP) revealed to improve by a greater amount when operating at a higher dry bulb temperature in the outdoor room. The reason for this increased improvement at higher outdoor temperatures was that the evaporative cooler was able to impart a larger reduction in the in dry bulb temperature entering the condenser. For example, at the highest dry bulb temperature testing condition, Test C (110oF), the evaporative cooler was able to provide 18oF of precooling. The effect of reducing the high-side refrigerant condition when precooling was applied to the condenser is a reduction in power consumption by the compressor, especially at higher outdoor dry bulb temperatures. For example, a reduction of 327 watts was observed at Test C, significantly offsetting the evaporative cooler’s 25 watt water pump power. The largest improvement in COP, namely 23%, occurred at the C Test conditions, which corresponded to the highest outdoor temperature of 110oF.
Citation
Coronado, Eric (2017). Improving Refrigeration Cycle Efficiency by Evaporative Precooling the Condenser Inlet Air. Master's thesis, Texas A & M University. Available electronically from https : / /hdl .handle .net /1969 .1 /173134.