Continuous capacity modulation, for example by varying compressor speed, is only one alternative to conventional cycling of vapor compression systems. Cycling the compressor at higher frequencies (~0.01–0.1 Hz) than conventional systems (~0.001 Hz) offers a potentially simpler and less costly alternative. Experiments were conducted to quantify effects of steady vs. pulsed flow on the performanc...

Abstract This paper presents a thermo-fluid dynamic analysis in micro-textured evaporator for loop heat pipes (LHPs) that has super wetting surface with ethanol on the basis of an experiment and modeling. In experiment, three kinds stainless steel plates various morphologies transfer surfaces were tested: normal flat plate, sandblasted micro-groove plate. The measured contact angles between 8.2...

The ability of zeotropic mixtures with a temperature glide to operate in liquid recirculation systems is investigated in this paper, and the preliminary results of an experimental comparison between the performance of R134a and of zeotropic mixture R32/Rl34a, (25/75 by mass) are presented. The perfonnance of Rl34a operating in dry expansion mode are also presented as baseline data. INTRODUCTION...

Small amounts of useful power may be generated in polar or subpolar regions during the winter period by placing a heat engine between a large body of water (near PC), acting as a heat source, and the atmosphere (near -25OC), acting as a heat sink. The scheme consists of a fuelless modular system operating on the Carnot cycle. Power is extracted by a reciprocating vapour engine drawing saturated...

This paper presents the experimental as well as the simulated performance studies on the transcritical CO2 heat pumps for simultaneous water cooling and heating; effects of water mass flow rates and water inlet temperatures of both evaporator and gas cooler on the cooling and heating capacities, system COP and water outlets temperatures are investigated. Study shows that both the water mass flo...

In this study an analytical model for open loop pulsating heat pipes (PHPs) is presented. The model predicts the effect of different parameters such as evaporator temperature, length of evaporator, filling ratio, number of turn and tube diameter on PHP's performance. The governing equations in two phase flow including mass, momentum and energy equations are solved for both one dimensional liqu...

Conventional control techniques are not able to accomplish the stable cooling in vapor compression air conditioning system. This paper describes the fuzzy models of refrigerating compressor, expansion valve, evaporator and condenser as basic elements of vapor compression air conditioning system. Compressor speed, delivery pressure, refrigerant flow rate, valve opening area, pressure difference ...

Preliminary note This paper presents the exergy destruction of an evaporator or a condenser or evaporator and condenser. The exergy destruction can be analytically calculated by using the same non-dimensional variables which have been used by its energy analysis. The one additional variable is the ratio of absolute input temperatures of both streams. This means that the given model enables the ...

Non-azeotropic refrigerant mixtures (NARMs) are investigated for a twotemperature level heat exchange process found in a domestic refrigerator-freezer. Ideal (constant air temperature) heat exchange processes are assumed. The results allow the effects of intercooling between the evaporator refrigerant stream and the condenser outlet stream to be examined in a systematic manner. For the conditio...