Experimental study on a cold storage system with a variable speed compressor

Selection of a compressor for a refrigeration system is generally done based on a peak load operating condition. The energy consumed by the compressor can potentially be reduced by regulating the compressor speed using an inverter. This experimental study investigates energy saving and performance enhancement potentials in an experimental cold-storage system when the electric frequency supply is reduced from 45 to 25 Hz, with a 5 Hz interval. The system is equipped with a compressor with a power rating of 3 HP (2.25 kW) and R22 was used as the refrigerant. The cooling load of the system was provided using an electric heater placed at the bottom of the cold storage chamber. Results show that the power input to the compressor was reduced when the electric frequency supply was decreased. The highest reduction in the compressor power input occurred when the electric frequency was decreased from 45Hz to 40Hz. The results also show that the coefficient of performance (COP) of the cold storage system was improved when the electric frequency supply was decreased. The largest COP improvement occurred when the frequency was decreased from 30 Hz to 25 Hz

Performance improvement using subcooling on freezer with R22 and R290 as refrigerant for various ambient temperatures

Vapor compression refrigeration cycle (VCRC) is widely used in freezers. In a simple cycle of the VCRC, refrigerant in the condenser exit is at liquid saturated line. If the refrigerant temperature in the condenser exit is further cooled to the subcooled region results in an increase in the cooling capacity due to low vapor quality of refrigerant entering the evaporator. The lower the refrigerant quality entering the evaporator, the higher the cooling capacity on the evaporator. The increase in the cooling capacity enhances the freezer performance. Subcooling uses liquid suction heat exchanger (LSHX) is applied to transfer heat from the exit of the condenser (liquid line) to the suction of the compressor. Because the temperature of liquid line is higher than that of the suction line, heat flows from liquid line to the suction line, results in the decrease in temperature of the exit of the condenser and the increase in the suction temperature (superheating). Consequently, the use of the LSHX is always followed by superheating on the suction of the compressor. The superheating causes an increase in the input power. As a result, subcooling using the LSHX is not always followed by the increase in the coefficient of performance (COP) of the freezer, depending on the type of refrigerant used. Refrigerant of R22 is widely used as refrigerant in the freezers. Because R22 has a high global warming potential (GWP), the near future this refrigerant must be phased out. Refrigerant of R290 (propane) is recommended as a substitute refrigerant for R22. The R290 is a natural refrigerant, abundant and relatively cheaper than that of R22. This paper investigates the use of LSHX subcooling in freezer with the evaporating temperature of -20 °C for various ambient temperatures, viz., 30, 35 and 40 °C using R22 and R290 as working fluids. It is well known that the COP of the freezer decreases with an increase in the ambient temperature. As a result, the use of the LSHX subcooler is expected to enhance the COP of the freezer for the higher ambient temperatures. There are three parameters, viz., the cooling capacity, the discharge temperature and COP improvement will be investigated in the present study. Numerical results showed that the increase in subcooling and ambient temperature increase the cooling capacity and COP improvements. In addition, the cooling capacity and COP improvements of R290 using the subcooling of LSHX were higher than that of R22 for all ambient temperatures. Also, the increase in degree of subcooling enhanced the cooling capacity and COP improvements. For R22, at the ambient temperature above 35 °C is not recommended using LSHX subcooling in freezers, because it will increase the discharge temperature above 90 °C. However, the use of LSHX subcooling is recommended for all ambient temperatures in freezer using R290, because the discharge temperature on the freezer is still below 80 °C

Investigation Of Modified Ejector Cycle On Residential Air Conditioner With Environmentally Benign Refrigerant Of R290

This paper investigates a modified ejector cycle (MEC) to further enhance the COP improvement of residential air conditioner (A/C), as compared to the standard ejector cycle (SEC). This paper also presents numerical and experimental studies of the MEC. Numerical approach of MEC performances was evaluated by using SEC cycle that had been developed by many researchers. In the experimental study of MEC, three motive nozzle diameters of 0.9, 1.0 and 1.1 mm were utilized. In addition, environmentally friendly refrigerant of R290 (propane) was used as a working fluid. The modeling results of residential A/C with the cooling capacity of 2.5 kW showed higher COP improvements of MEC than SEC for all entrainment ratios of the ejector. There was no COP improvement for SEC at a low entrainment ratio, whereas there are always COP improvements for all entrainment ratios for MEC. In addition, the experimental results showed the highest COP improvement of 16.67% was achieved with the motive nozzle diameter of 1.1 m

A review on sub-cooling in vapor compression refrigeration cycle for energy saving

Vapor compression refrigeration cycle (VCRC) is widely used in refrigeration and air conditioning (R&A) systems. Sub-cooling is used to improve the coefficient of performance (COP) of the R&A system by enhancing the cooling capacity. This paper presents various sub-cooling methods, which have been established and applied to enhance the performance of the VCRC. In a simple cycle of VCRC, the exit of the condenser is at saturated liquid line. Further cooling of the exit condenser to the sub-cooled region can result in an increase in the cooling capacity due to low vapor quality refrigerant entering the evaporator. As a result, the refrigerant absorbs more heat in the evaporator. The lower the quality of the refrigerant entering the evaporator, the higher the cooling capacity that is produced by the evaporator. This cooling capacity improvement results in an increase in the COP. In the present study, four subcooling methods are reviewed, which are liquid-suction heat exchanger, dedicated mechanical sub-cooling, integrated mechanical sub-cooling and condensate assisted sub-cooling. The advantages and drawbacks of each method, as well as future research direction in this research domain were discussed in detai

Effect of Regeneration Air Temperature on Desiccant Wheel Performance

Desiccant wheels are used as an air dehumidifier in air-conditioning and industrial applications. Desiccant wheel performance determines the size and cost of the whole system. A good desiccant wheel is one that saves energy usage. This article presents an experimental investigation on the effects of varying the regeneration air temperature, viz., 50, 60 and 70oC, on desiccant wheel performance. Three performance criteria were considered, namely condition of process outlet air, dehumidifier efficiencies and dehumidification rate. Two kinds of efficiency of the desiccant wheel dehumidifier were examined, namely thermal and dehumidification efficiency. Results of the experiments show that increasing the regeneration air temperature increases the dry bulb temperature of the process outlet air. However the moisture content of the process outlet air is reduced. The dehumidification efficiency of the desiccant wheel decreases with increasing regeneration air temperature, i.e., 46.7, 45.8 and 45.3 % for 50, 60 and 70oC, respectively. In contrast, the dehumidification rate increases with an increase in the regeneration air temperature, namely 32.6, 37.1 and 40.2 g/h for 50, 60 and 70oC, respectively

Evaluation Of Subcooling With Liquid-Suction Heat Exchanger On The Performance Of Air Conditioning System Using R22/R410A/R290/R32 As Refrigerants

This paper presents a numerical study to investigate the effect of subcooling with liquid-suction heat exchanger (LSHX) on the performance of air conditioning system using R22, R410A, R290 and R32 as refrigerants. In the near future, R290 and R32 refrigerants are projected to replace R22 and R410A as working fluids in the residential air conditioning. In this study, four parameters, i.e., the refrigerating effect, compressor work, COP and discharge temperature were investigated. In the numerical modelling, the evaporating and condensing temperatures were assumed constant at 5 oC and 40oC, respectively. The results showed that the COP improvements increased with the increase in the subcooling. R32 and R290 had the lowest and the highest COP improvement when subcooling was applied, i.e., 3.3% and 5.3% for subcooling of 5K and 6.2% and 10.2% for subcooling of 10K, respectively. Due to low global warming potential and almost identical refrigerant properties as compared to R22, system with LSHX and R290 has huge commercial potential as a replacement for conventional system in the futur

Quantitative Approach to Condensate from Residential Air Conditioners with Different Capacity as Drinking Water

During operation, the evaporator of split-type air conditioner (A/C) produces condensate water due to lower evaporator temperature, as compared to dew point temperature of the indoor air. So far, the condensate is considered unimportant and therefore being wasted. The split-type A/C is widely used in high-rise buildings, hotels, shopping areas, and even residential. The study aims to investigate the potential feasibility of the condensate to be used as for drinking water. Of course, treatment of the condensate is required before it can be used as a drinking water. The experiments were carried out in two cities, namely Bandung and Cirebon. Bandung represents a city with a cool climate, while Cirebon represents a city with a hot climate. The capacities of the A/C utilized in Bandung and Cirebon are 0.5 HP and 1 HP, respectively. The quantities of the condensate from the A/C were collected for 24 for hours. The quality of the condensate was benchmarked with guidelines/standard from PERMENKES NO 492/MENKES/PER/IV/2010. The benchmarking process involved testing and evaluation of 22 significant parameters related to water quality for drinking purpose. By utilizing waste condensate water, it is predicted that it can be a vital alternative of potable water in the futur

Single-cylinder 125 cc stepped piston engine for mobility and portable power generation applications

Two-stroke engines are far simpler than four-stroke engines from a physical perspective. For a given brake output, two-stroke engines are lighter, easier to work on, and provide higher power-to-weight ratio than four-stroke engines, making them suitable for small platform applications. However, conventional two-stroke engines have a reputation for generating smoke and unburned fuel, meaning they may not meet many emissions regulations, now enforced around the world. Thus, for many decades two-stroke engines have not been not favored, giving way to four-stroke engines for dominant applications, especially for mobile power-generation purposes. In the quest to improve the potential of such an engine, a group of researchers from the Automotive Development Centre (ADC), Universiti Teknologi Malaysia (UTM), has developed a 125 cc, air-cooled stepped-piston engine to demonstrate the higher power-to-weight ratio feature, apart from overcoming emission reduction. The engine is designed to mitigate the problem of mixture short circuiting, which is the major hindrance to combustion efficiency. To this end, they have incorporated a three-port stratification strategy into the engine. This paper provides an overview related to the earlier work done to integrate the necessary features and highlights some of the performance features of this unique engine design

Effect of compressor-discharge-cooler heat-exchanger length using condensate water on the performance of a split-type air conditioner using R32 as working fluid

The utilization of condensate water as a compressor-discharge cooler results in subcooling on the condenser outlet. On the other hand, a split-type air conditioner (A/C) with R32 as working fluid can provide higher compressor-discharge temperatures than other refrigerants used in the same A/C. Therefore, A/C working with R32, equipped with a heat exchanger by utilizing waste-condensate water as the compressor-discharge cooler, has promising potential to produce the largest subcooling effect in air-conditioning systems. The aim of this study is to investigate the effect of condensate water as the compressor-discharge cooler on the performance of an A/C using R32 as the working fluid with different sizes of heat exchanger. The experimental study was carried out on the A/C with a compressor capacity of 1.1 kW, using three different heat-exchanger lengths, i.e., 18, 20 and 22 cm. The results indicated that longer heat exchangers produced higher degrees of sub-cooling; the heat exchangers with lengths of 18, 20 and 22 cm produced average degrees of subcooling of 0.9, 1.5 and 4.5 K, respectively. Therefore, increments in the degree of subcooling generate improvements in cooling capacity, lowering the compressor-input power, and enhance the COP of the A/C. The average COP improvement of the A/C with heat-exchanger lengths of 18, 20 and 22 cm were 9.1, 14.4 and 27.3%, respectively