Condensation and evaporation heat transfer of R410A inside internally grooved horizontal tubesTransfert de chaleur à la condensation et à l'évaporation, pour R410A à l'intérieur des tubes rainurés horizontaux
Introduction
In recent years, many kinds of internally grooved tube have been developed to improve the performance of air-conditioning heat exchanger for HFC refrigerants and the experimental studies of the heat transfer characteristics of those tubes have been carried out [1]. Recently, Cavallini et al. [2] reviewed the many works concerned with the condensation heat transfer and pressure drop of these tubes. They compared the many experimental data published in literatures with previous correlations, and revealed the influence of compressor oil on condensation of refrigerants inside enhanced tubes. For the evaporation heat transfer, the authors [3] reviewed the proposed correlation which can apply to internally grooved tubes for HCFC22, R410A and R407C and suggested that the effect of the shape of micro-fin on heat transfer enhancement was not revealed well yet. Regarding the characteristics of pressure drop inside a tube, the empirical equations for smooth tube were proposed by [4], [5], [6] and those for micro-fin tube were proposed by [7], [8]. However, for the different kinds of internally grooved tube, it is difficult to estimate exactly pressure drop from these equations during both condensation and evaporation in heat exchanger. The purpose of this study was to experimentally obtain the characteristics of the pressure drop inside two different kinds of internally grooved tube with different micro-fin shape for HCFC22 and R410A, and also to experimentally verify the previous proposed equation for heat transfer coefficients by the experimental data that were taken at the same time when the pressure drop was measured.
Section snippets
Experimental apparatus and procedure
Fig. 1 shows a schematic diagram of the experimental apparatus, which is a vapour compression heat pump system, made up of a refrigerant-loop and two water-loops. The refrigerant-loop consists of a compressor (1), an oil separator (2), a four-way valve (4), a condenser (6), a mass flow meter (8), an expansion valve (10), an evaporator (11) and an accumulator (12). Each of the water loop is composed of a constant temperature water tank (15 or 16), a line pump (14), a flow control valve, a
Data reduction
On the reduction of the experimental data, the local evaporation and condensation heat transfer coefficient α is defined as:where Q is the heat transfer rate at each section which was obtained from the heat balance for the cooling/heating water flowing inside the annulus and Areal is real heat transfer surface area of internally grooved tube. Twi and Tr represent the arithmetic mean temperature of each section at the inner surface of the inside tube and the arithmetic mean
Local evaporation heat transfer coefficient
The measured local evaporation heat transfer coefficients α for HCFC22 and R410A are shown in Fig. 4(a) and (b) in terms of dimensionless form , where αL is the heat transfer coefficient of liquid component flowing alone inside a smooth tube which was calculated from the Dittus–Boelter equation [10] and x is vapour quality. The symbols ○ and • denote the measured data of HCFC22 for C tube and W tube, and the symbol ▴ denotes those of R410A for W tube, respectively. The solid and the dotted
Conclusions
An experimental study of evaporation and condensation heat transfer using two kinds of internally grooved horizontal tubes for HCFC22 and R410A were carried out.
The effect of shape differences on heat transfer enhancement between herring-bone grooved tube and the conventional grooved one are shown. The obtained heat transfer data indicates that the herring-bone grooved tube is more effective in enhancing evaporation and condensation heat transfer than the conventional spiral groove tube. It is
References (15)
- et al.
Heat transfer and pressure drop during condensation of refrigerants inside horizontal enhanced tubes
Int. J. of Refrigeration
(2000) - et al.
Evaporation heat transfer of HFCs refrigerant mixtures inside internally grooved horizontal tube
J. of the Tokyo University of Mercantile Marine (Natural Sciences)
(1998) - Inoue N, Goto M, Kandlikar SG. Flow boiling heat transfer with binary and ternary mixtures in micro-fin tubes. The 2000...
- et al.
A general heat transfer correlation for annular flow condensation
Trans. ASME, Journal of Heat Transfer.
(1968) - et al.
Two-phase flow in rough tubes
Trans. ASME, Journal of Heat Transfer
(1958) - et al.
Condensation of refrigerants HCFC22, HFC134a and HCFC123 in a horizontal smooth tube
Trans. Jpn. Soc. Mech. Eng. Series B
(1994) - et al.
Horizontal convective condensation of alternative refrigerants within a micro-fin tube
Enhanced Heat Transfer
(1999)
Cited by (0)
- 1
Member of IIR Commission B1.