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

源自六{维"论:文}网.加7位QQ3249`114 www.lwfree.cn

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