Thermal Cycle Analysis for an Application to Heat Transport System - Two Stage Condensation System

In the energy-saving research developments in recent years, many types of research project on high performance heat pump systems are under development It is required to estimate the thermodynamic performance of these thermal cycles on a common scale by applying an adequate method. a basic cycle of two stage condensation heat pump system is considered. Steady state conditions are analyzed for the given parameters of structural component characteristics and ambient conditions. Solutions are obtained by numerical methods, and the temperature, pressure, flow rate, thermal input, output power required are calculated by means of an improved simulation program. these results were compared with experimental results, and also the exergy analysis was made for the thermodynamic loss evaluation. INTRODUCTION In this analysis, an basic cycle of two stage compression two stage condensation system) is considered. Steady state conditions are analyzed for the given parameters of component characteristics and ambient conditions. Solutions are obtained by numerical methods, and the temperature, pressure, flow rate of thermal input and output, and compressor power re~uired are calculated by means of improved simulation program based on a single stage system analysis.· · · s) ANALYTICAL METHOD 1. Heat pump cycle balance points G) Evaporator water flow rate and inlet temperature, and condenser water flow rate and inlet temperature being set, heat pump system in a properly controlled state of compressor, condenser, expansion valve and evaporator, becomes to a steady state. This state is called as matching point or cycle balance point Fig.1 shows the concept of two stage compression two stage condensation heat pump system analyzed in this report Fig.2 shows a pressureenthalpy diagram corresponding to the system in Fig.l. The properties of working medium at the inlet and outlet of system components are on display in order to calculate the operation of the system. Point 6 and 9 are the state after the adiabatic compression at each stage, and point 7 and 10 are the state after the polytropic compression. In the following, two stage compression two stage condensation cycle is abbreviated as two stage condensation cycle. Basic construction of two stage condensation cycle is assumed to be a superposed form of two single stage cycles whose evaporators are common. In Fig.2, the working fluid entering in the first stage compressor with a flow rate of m 1 +m 2 are separated into flowrates m 1 and m 2 at the point 6, and discharges heat at the two condensers with the different temperature lebels, and meets at point 16, and constitutes a cycle. The flow rate ratio m z/ (m 1 +m 2) at the point of junction 6 and the two condenser pressure ratio P c ziP e 1 are given as initial parameters. Adiabatic compression and contant pressure variation at the condenser and evaporator are assumed, and the compressor work W 1 ,W 2, the thermal output from condensers, Q c 1 ,Q e 2 and the thermal input to a evaporator Q e are shown in the following, where, h denotes enthalpy. W 1 =m 1 (h s h s) W 2 =m 2 (h 9 h 6) Qol=hs-hl6 Qcz=h9-hla Q e=h 2 -h l (1) (2) (3) (4) (5) When cycle balances, by presenting the inlet and outlet state of each components on pressureenthalpy diagram, the working medium thermal properties neglecting a fluid momentum and energy losses are shown. These points are capable to be obtained experimentally. In the present analysis, 19 · thermal characteristic points are obtained numerically from the components and operating conditions.