Abstract
In areas with very hot weather conditions (50 to 60℃), the temperature and pressure of the air-conditioning condenser are increased considerably. This causes a decrease in the cooling capacity of the cycle and also causes an increase in the power consumption due to increased pressure ratio. In this work, an experimental and theoretical investigation has been done to improve the evaporator outlet fluid temperature through enhancing condenser performance. For this purpose, several modifications on the refrigeration system have been developed and tested to solve this hot weather problem. The air-side modifications include adding Spray Water above condenser (SW), wet Pad before condenser (Pad), and water Vapor Nozzle in the condenser air flow (VN). The refrigerant-side modification includes adding a pair of Heat Exchangers (HE) for exchanging heat between condenser exit and evaporator exit by using water-antifreeze mixture as a working fluid. A Water-Refrigerant(W-R) evaporator has been designed, manufactured, and compared with original Air-Refrigerant(A-R) evaporator performance. All air and refrigerant-side modifications have been investigated using both types of evaporators. The results indicate that the (SW) modification for enhancing condenser performance is the best method for COP improvement. The COP of (SW) system is found to increase at rate of (44.5 %) and (102.1%) as compared to system without modifications for (A-R) and (W-R) evaporators respectively. The outlet cooling temperature from evaporator has been found to reduce by about (30.3%) for (A-R) evaporator and (23.6%) for (W-R) evaporator. However, (HE+Pad) modification has been found as the best method for improving air side Nusselt number of condenser with an increase of about (4.7) times that of system without modifications. Ten new Nusselt number correlations have been predicted for each type of modifications under investigation by using both Engineering Equation Solver (EES) software and the experimental data. Cost-Benefit analysis in terms of life cycle cost, net present value, cost-benefit ratio, and payback period have been conducted. From the analysis, it can be concluded that using (SW) system will save a significant amount of energy with a payback period of less than five years.
Highlights
Air conditioning systems are considered as an indispensable for life requirements
The power consumption concern increased much more if the air-cooled condensers work in area with very high ambient temperature, as it happens in many Middle East countries
The results show that using (HE+Pad) and (SW+VN) modifications produce the highest condenser Nusselt number with an increase of about (4.7) times that of system without modifications
Summary
Air conditioning systems are considered as an indispensable for life requirements. Most of them are based on vapor compression systems that using R-22 with window type, split units, chillers and heat pumps. Because the cooling medium (air) is a natural and free source, the air cooled condensers (fin and tube heat exchangers) mostly used for low and average refrigeration capacities. In these air cooled condensers, the power consumption is a major issue in vapor compression cycle. The power consumption concern increased much more if the air-cooled condensers work in area with very high ambient temperature (between 50-60 0C), as it happens in many Middle East countries. In this area, the temperature and pressure of the air-cooled condenser will increased considerably. The high pressure and temperature of the air-cooled condenser will decrease the performance of the air conditioner considerably [1]
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