The Effects of Gravity on the Pressure Drop and Heat Transfer Characteristics of Steam in Microchannels: An Experimental Study

Minhhung Doan,Xuanvien Nguyen,Thanhtrung Dang

doi:10.3390/en13143575

Minhhung Doan, Xuanvien Nguyen + Show 1 more

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https://doi.org/10.3390/en13143575

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Abstract

Experiments were carried out to investigate the pressure drop and heat transfer behaviors of a microchannel condenser. The effects of gravity on the condensation of steam in the microchannels were investigated for both horizontal and vertical cases. For the experimental results, the pressure drop of vertical microchannels in the condenser is lower than for horizontal microchannels. In the case of the horizontal microchannel, as the mass flow rate of steam increases from 0.01 g·s−1 to 0.06 g·s−1, the pressure drop increases from 1.5 kPa to 50 kPa, respectively. While the mass flow rate of steam in the vertical microchannel case increases from 0.01 g·s−1 to 0.06 g·s−1, the pressure drop increases from 2.0 kPa to 44 kPa, respectively. This clearly indicates that the gravitational acceleration affects the pressure drop. The pressure drop of the vertical microchannel is lower than that obtained from the horizontal microchannel. In addition, the capacity of the condenser is the same in both cases. This leads to the performance index obtained from the vertical microchannel condenser being higher than that obtained from the horizontal microchannel condenser. These results are important contributions to the research on the condensation of steam in microchannels.

Highlights

In recent years, microchannel heat exchanger technologies have received much attention due to their high heat transfer efficiency
The results indicated that the heat transfer coefficients and pressure drop both increased with increasing mass flux and vapor mass quality and decreased with increasing saturation temperature
Where p1 is the pressure of steam at the inlet (Pa), p2 is the pressure of condensed water at the outlet (Pa), m is the mass flow rate of steam (g·s−1 ), h is the enthalpy, r is the latent heat of condensation, Cp is the specific heat capacity, T1 and T2 are the temperatures of steam and condensed water (K), and T3 and T4 are the inlet temperature and outlet temperature of cooling water (K)

Summary

Introduction

Microchannel heat exchanger technologies have received much attention due to their high heat transfer efficiency. The main advantages of microscale devices are their higher heat transfer coefficients and smaller characteristic dimensions. Previous studies focused on the characteristics of heat transfer and fluid flow at the microscale level in order to improve the design and optimize the performance of microchannel heat exchangers. Many studies on convective heat transfer and the pressure drop in internal microtubes and microchannels have been extensively implemented in the past decade. Tuckerman et al [1] investigated the heat transfer of water flowing under laminar conditions in silicon microchannels. Fayyadh et al [2] implemented experiments to investigate the flow boiling heat transfer of R134a in a multi microchannel heat exchanger. Three micro-condensers were studied: the microchannel condenser, parallel phase separation condenser, and conical phase separation condenser

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