A heat pump system requires proper refrigerant charge amount. Once refrigerant is charged into a heat pump system, its charge amount is fixed. For this reason, prediction of optimal refrigerant charge amount is very important in order to yield best performance. Too low charge amount degrades capacity of heat pump. On the other hand, excessive charge amount decreases coefficient of performance (...

In order to improve the coefficient of performance (COP) of a heat pump cycle by using carbon dioxide (CO2), an expander that recovers rotation power from the large pressure difference in the cycle to use the power to partially drive the cycle was developed. In the cycle a two stage rotary expander was adopted because the suction control mechanism is not necessary in it. In the development proc...

In this work, an unsteady state analysis of the compression cycle of a small hermetic reciprocating compressor for domestic refrigeration was carried out. The mass and energy balances were applied to the refrigerant inside the cylinder in order to determine the mass and temperature behaviour through the compression process. A specific onedimensional model of the valves was developed to calculat...

At present, the method adapted to analyze the phase equilibrium properties of refrigerant mixtures is as follows: Firstly, based on some experimental data of· phase equilibrium, the interactire factor bet~een the mixed refrigerants can be derived by using a equation of stalL Second!~ the rapour and liquid phase equilibrium properties are predicted by combining the mixed rule with phase equilibr...

Air conditioning contributes significantly to building energy consumption in hot climate regions. In addition to greater cooling requirements in hot climates, cooling equipment efficiency decreases with increasing outdoor temperature. Therefore, it is advantageous to develop improved technologies that can achieve higher efficiency at high ambient conditions. In this paper, two novel compression...

A capillary tube is widely used as an expansion device for small refrigeration cycles. Recently, immiscible oil is sometimes used in the refrigeration cycle to improve severe lubricating conditions and to prevent blockage of the capillary tube caused by the hydrolysis of ester oil. This paper discusses the influence of mixing of the immiscible oil with the refrigerant on the flow characteristic...

A series of tests were perfonned to verifY the transient characteristics of heat pump in heating and cooling mode when operating speed was varied over the 30 to 102Hz. One of the major issues that has not been addressed so far is transient characteristics during speed modulation. The model for cycle simulation has been developed to predict the cycle performance under conditions of increasing dr...

The demand for liquified natural gas grows as it is an energy resource that has more flexible means of transport than non-liquefied gas, and eco-friendly other fossil fuels. This paper focused on comparing five different mixed-refrigerant liquefaction processes to determine which one the most efficient in energetic economic terms four processing scales (20,000 kg/h 2, 4, 8 MTPA feed). Simpler w...