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垂直管蒸发式冷凝器英文文献和中文翻译

时间:2017-11-08 20:19来源:毕业论文
ABSTRACT Evaporative cooling is used to reduce temperature in different fluids in industrial and air conditioning processes. The processes of coolers involve two phase flow between air and water, the heat-mass transfer and its coupled proces
ABSTRACT  
Evaporative cooling is used to reduce temperature in
different fluids  in industrial and air conditioning
processes. The processes of coolers involve two
phase flow between air and water, the heat-mass
transfer and its coupled process. In this study, the
heat and mass transfer characteristics in a vertical-
tube evaporative condenser have been investigated.
A steady-state, one-dimensional model of cooler
performance was formulated and validated by
experimental measurement taken in this exchanger.
The heat resistance at  the air-water interface
predominates over all other heat resistance and the
heat and mass transfer coefficients occur at the air-
water interface. With the  enhancing experiment of
the spring inserts, the  heat and mass transfer
coefficients might be increased 5% to 17%. The
findings may provide more information to the design
of vertical-tube evaporative condensers.14994
KEYWORDS
Evaporative condenser, Vertical tube, Heat -mass
transfer, Heat resistance, Spring insert.
INTRODUCTION
The condenser is one of the key equipments in a
cooling system, which has many types, such as air-
cooled condenser, water-cooled condenser and
evaporative condenser. The evaporative condenser is
characterized by its little investment and exploitation
cost as well as economical used of materials and
space. The heat and mass transfer characteristics of
evaporative condenser are determined by the typical
summer design conditions and the air wet-bulb
temperature
[1]
. Thus, if properly designed, they may
reject heat at lower temperatures than dry heat
exchangers. Also, lower rejection temperatures than
the combination of water-cooled heat exchangers
could be achieved.
Previous researches in  the area of evaporative
condensers mainly focused on determining
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performance of horizontal-tube coolers, with and
without fins
[2-5]
. More recently, few studies on
vertical tube evaporative condensers were reported[6-
8]
, research on its heat and mass transfer was seldom.
In this study, heat and mass transfer in a vertical tube
exchanger with and without spring inserts has been
studied. A steady-state, one-dimensional model of
cooler performance was formulated and validated by experimental measurement. These results will be
offer insights to the design of this type of evaporative
condenser.
1 MATHEMATICAL MODEL
The evaporative condenser is composed of three
essential components: heat exchanger, water system
and air system. Heat transfers from the cooled fluid
into the water and from the water to air that flows in
the direction opposite to the water is forced by a
ventilator. Water evaporates into air, which carries
away the latent heat of water vapour.
In formulating a one-dimensional model of cooler
performance, some assumptions are made as follows.
(1)The process is steady-state.
(2)The overall heat transfer coefficient is based on
formulation of equations for mass and heat transfer at
the air-water interface.
(3)Mass and energy losses are neglected.
(4)Water and air are uniformly distributed in a plane
perpendicular to the direction of flow of respective
fluid, the same goes for all other thermal states.
Figure 1 shows the three fluids and the changes in
mass and intensive variables as they flow through a
differential length in a vertical-tube evaporative
condenser. We focus on the differential of length, dz,
one-dimensional, steady-state flow is assumed. The
equations are formulated based on the following sign
convention: flows of matter or energy going into a
control volume have opposite signs to those coming 垂直管蒸发式冷凝器英文文献和中文翻译:http://www.lwfree.cn/fanyi/20171108/15734.html
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