Research Papers: Evaporation, Boiling, and Condensation

Heat Transfer Analysis of Room-Temperature Finned-Tube Evaporator for Cryogenic Nitrogen

[+] Author and Article Information
Shun Ching Lee1

Department of Mechanical Engineering,  Kaohsiung University of Applied Sciences, Kaohsiung 80782, Taiwanleesc@cc.kuas.edu.tw

Tzu-Min Chen

Lien-Hwa Lox Cryogenic Equipment Corporation, Kaohsiung 81546, Taiwan


Corresponding author.

J. Heat Transfer 133(9), 091502 (Aug 01, 2011) (9 pages) doi:10.1115/1.4003924 History: Received April 14, 2010; Revised March 31, 2011; Accepted April 01, 2011; Published August 01, 2011; Online August 01, 2011

The behavior of cryogenic nitrogen in a room-temperature evaporator six meters long is analyzed. Trapezoid fins are employed to enhance the heat flux supplied by the environment. The steady-state governing equations specified by the mixed parameters are derived from the conservations of momentum and energy. The initial value problem is solved by space integration. The fixed ambient conditions are confirmed by way of the meltback effect. An integrated model is utilized to analyze the convective effect of two-phase flow, which dominates the evaporation behavior. Another integrated model is employed to determine the total heat flux from the environment to the wet surface of the evaporator. The foundation of the formation of an ice layer surrounding the evaporator is presented. If the fin height is shorter than 0.5 m, the whole evaporator is surrounded by ice layer. If the fin height is longer than 0.5 m, the total pressure drop of nitrogen in the tube is negligible. The outlet temperature is always within the range between −12 °C and 16 °C for the evaporator with the fin height of 1.0 m. For the evaporator with dry surface, the nitrogen has the outlet temperature less than the ambient temperature at least by 5 °C.

Copyright © 2011 by American Society of Mechanical Engineers
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Figure 8

Outlet temperature and total pressure drop of nitrogen for various mass fluxes: (a) outlet temperature and (b) total pressure drop

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Figure 7

Enthalpy and temperature of nitrogen: (a) temperature; and (b) enthalpy

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Figure 6

Wall temperature of the tube

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Figure 5

Pressure and heat transfer coefficient of nitrogen: (a) heat transfer coefficient; and (b) pressure

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Figure 4

Thickness of ice layer at various wall temperatures, Tw,Al, and at various heat fluxes or fin heights when ξ=3m and pv= 2.217 kPa

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Figure 3

Heat transfer coefficient of water layer at various wall temperatures, Tw,Al, and at total heat fluxes or fin heights when ξ=3m

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Figure 2

Illustration of trapezoid fin

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Figure 1

Illustration of finite volume



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