Experimental Study on a Cold Storage System with a Variable Speed Compressor Nazri Kamsah a , Haslinda Mohamed Kamar b , KASNI Sumeru c , and Tandi Sutandi d a Faculty of Mechanical Engineering Universiti Teknologi Malaysia, Johor Bahru, Malaysia Tel : (+607) 5534749. Fax : (+607) 5566159 E-mail : nazrikh@mail.fkm.utm.my b Faculty of Mechanical Engineering Universiti Teknologi Malaysia, Johor Bahru, Malaysia Tel : (+607) 5534748. Fax : (+607) 5566159 E-mail : haslinda@mail.fkm.utm.my c Department of Refrigeration & Air Conditioning Gegerkalong Hilir Ciwaruga, Bandung 40012, Indonesia E-mail : sumeru84@gmail.com d Department of Refrigeration & Air Conditioning Gegerkalong Hilir Ciwaruga, Bandung 40012, Indonesia E-mail : ade.tandi@gmail.com ABSTRACT 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. Keywords Variable speed compressor, energy saving, inverter, cold storage system, COP 1. INTRODUCTION There are four basic components in a vapor- compression refrigeration cycle (VCRC): a compressor, a condenser, an evaporator and an expansion device. In a small air-conditioning system the compressor typically consumes nearly 90% of total energy input while in a central-type system the compressor consumes approximately 72% of the total energy input [1, 2]. A thermostatic expansion valve (TXV) is traditionally used to regulate the degree of superheating and cooling capacity of the system [3]. The device also regulates the evaporating pressure and the refrigerant mass flow rate. The opening of the TXV depends on the cooling load demand. However, the degree of superheating and refrigerant mass flow rate cannot be controlled independently. In a refrigeration system the compressor capacity is usually chosen to meet the peak cooling load demand, which is a combination of internal and external cooling load. The internal cooling load could reach the peak value at any brought to you by CORE View metadata, citation and similar papers at core.ac.uk provided by Universiti Teknologi Malaysia Institutional Repository