换热效果最好； 而从减阻的角度看，则是和圆管具有相同管周长的椭圆管的减阻效果最好，

在实际应用时 可以根据具体强化换热与节能减阻要求加以合理选择。

关键词：

CO

2

制 冷剂；跨临界循环；流动与换热；强化换热；场协同原理

Experimental Study on CO

2

Residential Air- condition System and

Numerical Simulation on Enhanced Heat Transfer of Heat Exchangers

Tao Yubing

ABSTRACT

In recent

years, the problems

of

environment and energy

have been more and more

serious.

Ozone depletion, greenhouse effect and energy crisis have become the main challenges for human

being. The refrigerants used in refrigeration and air- condition systems not only make ozonosphere

destroyed seriously but also cause great greenhouse effect. Looking for alternative refrigerant has

become an exigent task for refrigeration industry. Due to the favorable thermophysical properties

and benign environment effects, CO

2

has attracted extensive attentions in recent years. On the other

hand, the requirement for energy is more and more increasing and the combustion of fossil energy

exhausts a large amount of greenhouse gas which aggravates the greenhouse effect. We are facing

the threats of fossil energy drying up and environmental pollution. How to effectively utilize energy

and efficiently protect ecological environment has become the key issue for all the countries. So it

is very important to study the enhanced heat transfer and decreased pressure drop characteristics of

the heat transfer equipments which are widely used in many fields.

The

objectives

of

present

dissertation

are

focused

on

the

alternative

refrigerants

of

air-condition

system

and

energy

saving

of

heat

transfer

equipments.

The

corresponding

experimental and theoretical studies are performed. In the experimental study, the domestic first test

rig for the performance of CO

2

residential air- condition system is set up. The effects of operating

conditions on the heat transfer and fluid flow performances of heat exchangers and the system total

performances are experimentally investigated. The throttling loss, effect of throttling loss on COP

and influencing factors on throttling loss are analyzed for the CO

2

transcritical cycle with an inner

heat

exchanger.

Some

reliable

approaches

to

reduce

throttling

loss

and

improve

the

system

performance

are

presented.

In

the

theoretical

analysis,

a

hybrid

grid

generation

technology

is

proposed

based

on

body

fitted

coordinates

and

block

structured

grid

generation

method,

three-dimensional

grid

generation

and

numerical

simulation

codes

are

developed.

Then

the

heat

transfer and fluid flow characteristics of wavy fin-and-tube heat exchangers which are widely used

in

industry

fields

and

air- condition

systems

are

numerically

studied.

The

effects

of

geometric

parameters and operating conditions on the total heat transfer and fluid flow performance and fin

efficiency

of

the

heat

exchanger

are

examined.

Then

the

distributions

of

local

heat

transfer

coefficient and fin efficiency on the plain plate fin and wavy fin surface are examined. Based on the

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