The present situation and development of domestic
fan-coil
1 Prefacer
These years, the fan-coil industry of our country
has got a rapid development, from the thousand in the
early eighties ,the recent annual output have increased
to more than 500,000.Even though, the performance of the
production remain on the level of seventies. The rapid
development under low made the prospect of this industry
not well.
In the middle of the
nineteen eighties, the foreign fan-coil industry, such
as several companies of the US, have finished the
renovation of the production, and put forward totally
fresh manufactures. Compared with this ,that time, we
only enjoyed on the progress of the parameter closing
with the foreign’ such as cooling & noise level
but neglected the real distance in the performance and
using affection. As a result, this updating made no
reflection on our air conditioner industry. In fact, the
new generation of the foreign fan-coil is much advanced
than ours not only on performance, but also on the kinds
and using on air conditioners.
2 The distance of our
fan-coil from the foreign
Air condition is depending
on air condition equipment or other terminal instrument
to blow some different temperature air in continually or
intermittently, in order to keep the balance of the
temperature and humidity of the room. When the air
quantity and the cold load reach a balance, accuracy air
condition will lie on the blowed air temperature and air
exchanging frequency. The accuracy of air condition will
be higher with the smaller air temperature deference、less air-changing frequency and smaller temperature
gradient and fluctuation. So ,in the GBJ19-87<heating
& drafting and air condition design rules >,there
are exact prescriptions of the max air temperature
deference and least air changing times in different
accuracy required air condition rooms, such as
comfortable air condition in summer, the blowed
temperature deference shouldn’t more than 10℃,air change times shouldn’t less than 5/h. Cooling
quantity only reflects the fan-coil capacity to
eliminate the cooling load, the effect of air condition
depends on the real blowed air quantity and enthalpy
deference. From theory, only to choose the different
unit in different using situation could obtain the best
air condition effect.
The industry criterion of
our country JB/T4283-91<fan-coil unit> has carry
out a general principles on the air quantity、heating amount、cooling amount per fan、noise level 、water obstruction and other parameters, further more,
the suit standard JB/T50056-95<the quality degrees of
fan-coil unit > stipulates the quality degrees should
be divided by the above parameters, which bring the bad
tendency on real performance and using effect ,caused by
the simplex performance of domestic fan-coil, low
attenuation ,high enthalpy deference, low air amount as
well as too high blowed air temperature.
Contrasted with this, the
foreign companied paid more attention on rising the
performance and effect of products. At present, they
could not only manufacture 2 platoon , 3 platoon , (2+1 ) platoon different cold and heat
single fan-coil or unit ,but also could supply blow
plenum attenuation products with high plenum attenuation、standard attenuation 、low noise and etc. So, under the same blowed air
quantity ,there are various products of different plenum
attenuation and enthalpy difference. Compared with this,
the distinction is oblivious with the single type low
plenum attenuation 、high enthalpy difference domestic fan-coil.
3 Improving
the
recessed fan-coil
blowed air plenum attenuation
The sale of recessed
fan-coil unit occupies above 70%~80% of the total
portion. Its performance represents the overall level of
the fan-coil products.
Our industry standards JB/T4283-91:
fan coil (non-static pressure units), the wind in order
to make the volume of water, and poor zero static
pressure conditions into testing. The wind amount of
fan-coil (non-plenum attenuation units) should be tested
under the situation of no water flow and the attenuation
difference of input and output. As the recessed units
should be installed backward air grid, filter , short
air tube, fan-coil congeal gel and filter dust, all of
them will bring larger wind force, as a result, the real
wind amount decreased. Disadequant wind amount will
cause the decreasing of cooling supply. So , the
parameter of fan-coil
nominal wind amount and cooling capacity which accord
the JB/T4283-91 rules could not be reproduced during the
practice.
When the standard was
revised in 1990 , though a reference of attenuator
fan-coil units had been increased, index such as wind
amount , cold quantity , noise level were all stipulated
according to the non attenuation units, in addition, no
corresponding modification was made, so
units with attenuator were unable to pass test of
standard .
According to sector standard
,the recessed units our companies product at present are
all without air plenum attenuator , not only with low
blowed air plenum attenuation level , actual wind amount
seriously insufficient, but also the products’ volume
and weight is relatively large, generally the products
of the same more type than foreign countries are getting
large 50- 100%, raw materials and resources consumption
are all much more than the foreign products. Improve
overall level of domestic fan-coil, the primary is to
improve blowed air plenum attenuation level of recessed
fan-coil units.
4 To product fan-coil
with different kinds of enthalpy
When choosing fan-coil, we
should know that cooling capacity depends on calculating
cold load ; Wind amount must meet the demands of
temperature difference of blowing ,air exchanging
frequency and air distribution . The air conditioner
rooms of different demands in cold load and usage, the
match situation of the wind amount of cold quantity
should not be unalterable. The energy
swiftly condition, orientation or enclosing and
protecting structure differences ,etc. could cause the
differences in cold load, even in the same air
conditioner required the room the same as net volume.
Obliviously, the only use of fan-coil with different
enthalpy could meet to the demand on cooling quantity.
So, using the fan-coil of different enthalpy, even
choose the fan-coil units of different cooling quantity
according to cold load, it could cause the over-change
of room temperature gradient and fluctuating range in
the low load level room, as the insufficient of wind
amount and wind-changing times,furtherly,it reduce the
precision and comfortableness of the air conditioner; to
be compared, using the same wind quantity units
couldn’t guarantee warm and humidity demands under
insufficient cooling supply in high
load level
room. So in the air conditioner rooms of different
service conditions and requirement, we should select the
fan-coil with different enthalpy for use respectively.
5 To develop the two-platoon fan-coil
The reducing difference in
temperature of blowing, as well as increasing the times
of air exchanging is helpful on improving precision and
comfortableness of the air conditioner. Under the same
cooling quantity, adopting little difference in
temperature, large blowing amount, will obtain a better
air conditioner affection than the opposed ones, in the
same time, it can contract heat-conduct area of fan-coil
and external dimension of the units at the same time. In
charge of the fan-coil with low enthalpy , two platoon
ones received a rapidly development and abroad
popularize in recent years.
In the middle of the
eighties last century, three platoon 42E/J series which
were produced for many years were replaced by two
platoon 42C/V series fanfoil by Company successfully.
Some foreign producers used two platoons in charge of
difference series aircrew products replacing a
traditional singular three platoon products.
5.1 The advantages of two
platoon fancoil
5.1.1 Cold supply not less
than the traditional three platoon fancoil
The heat emission proportion
of the two-row coil is 1/3 less and the air supply
enthalpy is comparatively low, but the resistance is
weak, the air is strong, besides with the design of the
strengthen of heat emission and the improvement of the
coil, the cooling supply is equal to or more than the
three-row coil.
5.1.2 The improvement of the
air-condition
The two-row coil made by the
abroad producers ， the average enthalpy
difference is 8.5～14.5kJ/kg , the
average air intake rank is 6～10℃ which will meet almost all the demands. The home-made
coil if calculated with the parameter in name the
enthalpy difference would be 16.5kJ/kg ，the air requirement of
the recessed unit is 20% lower than the unit in name,
the actual enthalpy difference would be more than
20kJ/kg , the difference air temperature of the air
intake would be more than 15℃，that would be deviated from the GBJ19-87 standard, say
nothing of the standard of the high accuracy
air-condition.
The enthalpy difference of
two-row coil and the air intake temperature are low, the
air is strong, the frequency of air exchange is high,
the effect is usually better than the three-row coil
unit.
5.1.3 High efficiency and
power saving
The actual air capacity and
cooling of the home-made recessed coils are lower than
the number in name, therefore a lot of the air-condition
designers choose the products according to the
medium-gear parameter, that would enlarge the unit type,
meanwhile the primary investment and capacity of the
cooling water system include cooling unit , pump,
cooling tower and the pipes.
The air intake pressure of
the two-row coil is high and the air is stronger which
enable the unit to be qualified of the name that it is
called, the customer could choose according to the
high-gear parameter to get the type , then they could
reduce the types they need and the capacity and power
consuming of the cooling system. Therefore if two-row
coil’s system is used the primary investment and the
operation fee would be lower than the three-row unit.
5.1.4 Reduce the cost and the
resource consumption
The two-row coil not only
save 1/3 non-ferrous metal like copper pipe and aluminum
foil, lower the cost, but also could replace the
three-row unit which could reduce the raw and processed
material and the power consumption greatly, the customer
could also save lot of primary investment. It is obvious
that the production and popularization of the two-row
coil has both the social and economical benefit.
But the enthalpy difference
of the two-row coil is low, the capacity of the
dehumidification is poor, so in the area where the
latent heat load is high , the three-row coil unit is a
better choice.
5.2 The design feature of the
two-row coil
In recent years , the
two-row coil is popular in abroad , 以特灵、约克 are two examples ….the 1/2〃 type made by some producers has been washed out during
the 1980s. the 5/8〃2×6 type has little
resistance, it fits to the high buildings.
5.2.1 The multi-water pass
design of the coil
目前我国生产的三排管盘管，不论长短，都采用相同的三进三出水路。两排管过流断面积小，为了降低水阻力、提高供冷量，不同长度的盘管须采用不同的水路设计。如特灵2×6盘管，200～600风量的中短盘管为二进二出；800风量以上的长盘管为三进三出。开利的2×8盘管，则分别采用了二进二出、三进三出和四进四出三种不同水种。图2是某公司的2×8盘管水路设计。图2-a为二进二出，用于200、300风量；图2-b为三进三出，用于400、600风量；图2-c为四进四出，用于800、1200风量。
5.2.2 Provide various air plenum
by changing the generator speed
The high and standard air
plenum and the silent coil that made in abroad is
realized by the change of the generator speed. If we use
different generators, then we will have many types which
will make the storage cost increased. All of these will
do no good to the production management and the
maintenance of the after-sale service. So all the
producers choose the five-times speed generator.
5.2.3 General use of units
Different multiplatoon fan
coil should be designed to assure the general use of
units, decrease the varied kinds of units, convenient
operated, shorten the manufacture and stored period,
decline cost.
6 Revise the current
industry standard
The fancoil industry
standard was set in the 80s, carried out in the year of
1990, which reflected the understanding and products
level of fancoil in the 70s and 80s. But as the curve of
planned economy and in ignorance of the development
trend of foreign fans, there still exist some unsuitable
content and mistakes. If it would not be revised in
time, it would hinder the products development.
6.1 Revised the standard
flow volume level and test condition
Customers should according
standard flow volume to choose fancoil, assuring the
real flow volume agree with the standard flow volume is
the basic requirement of products.
The foreign fancoil standard
flow volume refers to the one under the normal
installation and using condition, to the recessed unit,
it refers to the flow volume under the outside static
pressure. In the ARI440-84 principle 《room fancoil air condition》of American air condition and cooling association, it
disciplined that standard fancoil flow volume should be
measured under 12.4Pa outside static pressure with out
air grille and filter. In domestic rules, the standard
flow volume (staticless unit) refers to the one measure
when there is no outside pressure, so the real flow
volume would be lower than the standard one. So we
should make our rules connect with the international
ones, to improve domestic fancoil performance and make
our products could engage into the international
competition.
6.2 Release the
restricting of products cooling volume
When the industry rules
drafted, our fancoil production was little, craft was
disadvantage, performance and quality was all instable,
so the limited parameter of cooling volume and noise
played an active part to assure the products quality.
Nowadays, as many large companies have introduced
foreign advanced high efficiency fancoil,
plate processor equipment and produce lines,
their products quality are basic stable, so the
restricting of cooling volume lost active sense of
guarantee products quality, what’s more , it may
become a obstacle of the renewing of products.
JB/T4283-91 belong s to
suggested standard, but it has been executed by force,
the products which could not along with the standard
would be judged to be the “unqualified products”. So
the administration forced and monopolized standard was
the fundamental reasons of the stagnancy of fancoil
development.
6.3 Release the
restricting of products noise
The development obstruction
of high static pressure fancoil mainly come from the
noise level standard, and it also reflected that there
still existed some mistake understanding of the air
condition noise from domestic companies and customers.
The fancoil noise is
combined aerodynamic noise and machinery noise.
Machinery noise level depends on the rotation unit
processor, dynamic balance, assemble exactitude, aw well
as products quality; aerodynamic noise is relative with
the input air static pressure and flow volume. The
aerodynamic noise is higher than machinery noise, so the
whole noise level could not reflect the quality of
fancoil, as low noise level don’t mean high quality.
For example, a large flow volume, high pressure fancoil
has higher noise than the moderate pressure and low
noise unit, but that does not mean the first one has bad
quality than the last one. So, limited the noise not
only do help to guarantee the products quality, but also
limit the enhance of air static pressure and flow
volume, and directly influence the effect of fancoil.
Different situation demands
different noise level. Large markets or shops do not
need so low noise as the hotels. So the rule demanding
all fancoil should reach the same noise level is
irrational. It would not only satisfy the demand of high
static pressure and large flow volume fans, but also
could make enormous waste of material and energy. In the
foreign rules, no such limitation had been set.
6.4
Standard of “single fan
power cooling capacity” is tenor mistake
Except wastage, the input
power is all transform to convey air. It has no
relationship with the heat supply of fancoil, so the
standard of “single fan power cooling capacity” has
no physical meaning, but the mistake using of power
transform coefficient EER and performance parameter COP.
And this standard is harm for the development of high
static pressure low enthalpy margin products, so these
rules should be deleted in the revision.
7 Conclusion
①According to the industry
standard, the domestic fancoil all have the
disadvantages as, low statistic pressure, high enthalpy
margin, large air temperature difference, simple
performance, inadequate flow volume, and the disagree of
the real performance with standard parameter, they could
not reach the design requirement, ideal air condition
effect should not be obtained.
②The current industry
standard is the main reasons of the stagnancy
development of domestic fancoil: revise industry
standard, connect it with international advanced ones to
accomplish the precondition of products renewing and
engaging the international air condition market.
③Enhancing the input air
static pressure, developing the leading two platoon
fancoil various enthalpy margin and different input air
static pressure products is the development trend of
domestic fancoil.
④Cooling volume only reflects
the cool load elimination capacity of fancoil, which has
no direct relationship with the air condition effect;
the required real flow volume and enthalpy difference is
the crucial elements determined air condition effect.
⑤Noise level could not
reflect the fancoil quality; low noise level does not
mean high quality.
The
influence on fan industry after joining WTO and
concerned trouble solution TOP
Ⅰ.Briefing of WTO
WTO is the largest
international trade system. Contrast with tariff and
trade agreement, it is an authority international
economic organization with law effect, belongs to the
three international economy organization.
WTO agreement is the successor one of tariff and trade
agreement, what’s more, it expand the administration
range of tariff and trade agreement. Tariff and trade
agreement suits to the goods trade, besides this, WTO
agreement added service trade, investment measure and
rights received protection. The tenet is: basing on the
improving of life level and assuring employment, enlarge
the goods production and trade, according the continuous
development principle to realize the best distribution
of resources; make effort to guarantee the trade
development proportion of developing countries, making
it suit to their economy. WTO is a integral, animated
and eternal multilateral trade organization.
There are 135 countries in
WTO, the trade amount among the members occupy 90% of
the world trade. The independed tariff district could
apply to join in. the application could be passed if two
third members voted pass in minister above council. In
July, 1986, our country replaces the treaty country, and
we applied to join in WTO in 1st, Jan, 1995
when WTO replace the tariff and trade agreement. After
contracting double-lateral agreement with the US in 15th,
Nov, 1999, the joining in pace speeded. According the
assignment of WTO China business team, 36 members wanted
to talk with us. Now, we have contracted with 25
members. And there are 29 independed law processors. 25
ministers declarations, determine and understanding in
the WTO agreement. All the documents should along the
follow four principles.
1、Indiscrimination
trade
No discriminated rules could
be adopted during the trade among the members. It mainly
contains Most-favored-nation treatment and civil
treatment.
The best country treatment
refers that one member supply another member the best
country treatment, the member should supply all of the
members the same treatment in the WTO. No discrimination
trade could be done. All the members are equal in law,
and could enjoy the benefit equally.
Civil treatment refers that
if one country (district) supplies the treatment to
their domestic products, the same treatment should be
applied on the imported products from the member
countries. That is after the handing of tariff, all the
imported products should circulate in the market in the
same with domestic ones.
The above two principles
still be effective on other trade rules.
2.Expand the passing
standard
This rules contains tariff
and un-tariff rule. WTO allows the member countries to
adopt the tariff ways to protect their economy, but the
tariff should be the lowest. After negotiation, the
allowed lowed tariff should be changed by single part,
and it also suits to other members.
Un-tariff rule refers to the
quota and license of imported goods.
3.Fair competition
All the competition should
be fair, unfair trade ways should not be adopted. No
dumping business, allowance should be carried out. The
trade police, laws should be unified and clear.
Dumping trade refers the
price which is lower than the cost, with that price
products were sold to the international market.
Allowance is the allowance to the export products from
their government and professional association during the
produce, processor, trade and exports.
WTO emphasized if the
dumping and allowanced products bring harm to the
agriculture and industry of imported countries, the
import countries could accuse the export countries of
their dumping and allowanced products. When the accusing
was check and verified, anti-dumping and allowance
methods or tax could be carried out.
Clarity should be improved: ①. the member counties should declare their laws, statues,
administration regulations and judge execute r\of the
trade, to make other members governments and managers
know and familiar.②. Trade agreements and ordinance contracted by the members
all should be declared.③. Trade polices should be uniform in the country, all the
laws, statutes, administration regulations and judgments
should be executed rationally. ④. Trade assessment system should be set.
4.Encourage the
developing countries to reform their economy and supply
them some privilege principles
WTO Encourages the
developing countries to reform their economy and supply
them some privilege principles. Three fourth members in
WTO are developing countries, many of them have reform
their economy actively. Uruguay has declared that
developing members will take on most of the duty as the
developed members. But a transition period should be
supplied to the developing members to apply WTO
stipulations, tax and allowance could be flexible to
them; developing countries should give no trade
privilege to the developed country; tariff decreasing
police could be supplied between developing countries
with no need to apply to developing countries;
developing members could enjoy General preference.
General Preference is a tariff preference given by
developed countries to developing countries, which is a
general, indiscrimination and un-reciprocal rules to the
end or half-end products, the tax is lower than
Most-favored-nation treatment.
Ⅱ.Influence on fan
industry after joining WTO
Taking part into WTO puts an
importance effect to refine our international trade
environments, expand exports, introduce foreign capital,
advanced technology and equipments, improve
international economy cooperation, speed the
reformation, promote the mature of our communism economy
system, and enhance our international status. But while
enjoying the rights, we should also take on the duty of
stipulated by WTO, and the more open market would
influence the development of some industry, and bring
them intense situation.
Fan industry is a part of
general machine, so, firstly we analysis the influence
on machinery products.
1. As labor force density products or low cost products have the
advantage on price, and these products have possessed
certain competition in international market. Joining WTO
could expand exports, so the open of domestic market has
basically no damage on these products.
2.2. Capital density and
technology density industries would be impacted. ①. Some domestic companies have cooperated with world
famous companies and transnational corporations, so
their products are advantage on technology and price
(their price is lower than the exported products), so
after the open of domestic market, they would not be
impacted only when there are more strong competition; to
be opposed, as the combination companies enjoy the
“extra-civil treatment” and their imports units tax
would be low, their cost would be lower and have much
more competition. ②. Though the products technology has some distance
between the foreign ones, they possess obvious price
advantage. So the products of these industries would not
be hardly impacted after the opening of market.③. High new technology industry and new developed high new
technology industry have not possessed competition, or
their products prices are higher than the international
ones, so they would be impacted.
3. A group of companies
would be reorganized, transformed or abrupt
As too many small scale
produce companies which don not possess certain economic
scale and competition, and faced with difficult
position, these companies merged, reorganized,
transformed or abrupt.
To sum up, the joining into
WTO, bring us both benefit and challenge. To machinery
industry, some vehicle, and high new technology products
would be washed up during the competition. For the whole
and long-range interesting of our country, it is the
expense we must pay. At the same time, our government
would not sacrifice national benefit, as a developing
country, we need a transition period to performance some
duty. The practice has proved that after joining WTO, no
industry has been broken, but promotes the development
of our economy.
Fan industry can be divided
into two categories, so the influences from “joining
WTO”have two different situations.
1.Turbocompressor and Air
blower
There are not many
enterprises that produce this kind of product, but it
has represented the technical level of fan profession.
This kind of product is situated between the technical
level which is mentioned above and has the certain
disparity with the oversea product , but the disparity
is not very big, moreover the product’s price has the
obvious superiority (mainly refer to centrifugal blower
and general-utility centrifugal compressor), and the
high-tech industry and the new development high-tech
products (mainly refers to ethylene installments
centrifugal compressor, the natural gas pipeline
compressor, the high-pressure field gas injection
compressor and the large air separating equipment
compressor, the output of which are above 600,000ton
each year ), there are still do not have the competitive
ability between these two.
The former situation
will be attacked not serious after the market opening.
But the enterprise produces this kind of product have to
get the sense of urgency, which puts emphasis on
enhancing development and innovation ability, enhancing
the product technology content and the class, reducing
the disparity with oversea products.
The
latter kind of situation will be under a bigger impact
after the market opening.
2.Middle and small size
ventilator for general use
This kind of products is
overwhelming majority of the fan professions with large
quantity and broad areas, which is equal to the
situation mentioned above that has lower product cost
and price superiority. After entering World Trade
Organization, it will be advantageous to the expanded
exportation, the domestic market opens does not pose the
threat. For example, the famous ventilator enterprises
in the world mainly have German TLT Corporation,. 英国豪登公司、日本荏原制作所.Shanghai ventilation equipment factory has already
introduced the German TLT technology, 英国豪登公司has established the
single-venture enterprise in China, already participated
in the domestic ventilator market competition.
At present ,The Japanese
merchant ventilator product price is 2 times of domestic
product, after entering the World Trade Organization,
the customs duty has reduced, but its price still 50% ~
60%higher than the domestic product. Thus explained,
this kind of product after entering the WTO cannot form
a more tremendous influence to the domestic market. But,
this kind of product has a general problem; generally
speaking the surface quality is bad. The plate work, or
the paint, most of enterprises' product outward
appearance quality cannot achieve the exportation
request. According to our fan profession association
incompletely understanding, the enterprises produce this
kind of product, only the Zhejiang Shangfeng group
company, Beijing Xinghua Ventilation Company, Lushun
Blower Company, Beijing Jingfeng Ventilation Company,
the product outward appearance quality of which are
better, have achieved or approached exportation request.
Ⅲ.Countermeasures
and suggestions should be adopted
"Joining WTO”is not
only a opportunity, but also a challenge. We must fully
use the rights and the favorable conditions, developing
international economy cooperation, expanding
exportation, using foreign capital; Simultaneously
should study some enterprises' impacts earnestly, using
the 5 ~ 6 year transition period, readjusting the
structure, speeding up the development.
1.Understand the World Trade Organization agreements,
enhancing the foresightedness and the initiative
First, the leaders of
various fan enterprises must strengthen the study,
understanding the World Trade Organization agreements
and the actual situation, studying how to use the basic
principles of WTO, developing international economic and
technological cooperation; Next, analyzing after our
country "entering WTO ", whether the products
can take a share in the domestic market, whether the
favorable conditions can be used for expanding
exportation, whether there are superiorities in the
quality and the price aspects, whether set up the
factory abroad or material processing equipment ; then,
some enterprises that technical levels, the quality and
the price are in the inferiority in the competition, is
going to be under the impact, must fully use the
transition-period, forms the economical scale, develops
the variety, improves the quality, reduces the cost,
enable themselves to have the competitive ability. If in
the transition-period the improvement is also difficult,
the decisive decision-making, the structure adjusting,
the new outlet-seeking are needed.
2.Set up the extroversive developmental strategy, expand the
exportation vigorously
After" entering WTO",
our products for export can be allowed to enjoy the
World Trade Organization member's most-favored nation
treatment, also may enjoy preferential benefit system in
certain developed countries (to be lower than
preferential duty, at present there are 28 countries of
this kind altogether, our country has obtained this
treatment from 21 countries), and obtains the fair trade
treatment in these markets, the export environment will
be improved greatly. Our government has taken many
preferential measures to the mechanical and electrical
product exportation, enhanced tax reimbursement, after
" entering WTO ", the foreign trade rights
will change speed up from the examination and approval
system to the registration system, the enterprise may
directly open to the international market, will maintain
independent management, management scope will also be
larger.
3.Expand the international economic and technological
cooperation positively
After " entering WTO
", economic and technical cooperation environment
between our country and the members of World Trade
Organization will have a larger improvement, our
investing environment also get a further improvement,
will be more advantageous to the attract foreign
capital, advanced technology and the equipments, will
develop joint venture, the cooperation or bring into
technology through the technique trade union. We should
take the opportunity, choose well-known foreign
manufacturers with competitive ability and abundant
capital, develop negotiations and cooperation,
especially aim at the products with large import
quantity and higher technical content, exchange the fund
and the technology with market, raise the technical
level and the management level.
4.Reinforce the momentum of
structure adjustment
According to the Central
Party Committee principle of “take the public
ownership system as the main body, the other kinds of
systems develop communally, ｂｅ ｆｌｅｘｉｂｌｅ ｏｎ ｓｔｒａｔｅｇｙ", following four
mainly measures should be taken:1, the joint stock
system reform, the enterprise that has the conditions
strive for the stock to go on the market, mid- and
small-scale enterprises realize the system of ownership
multiplication; 2, cooperate with foreign merchant on
products that has big import quantity and higher
technical content product, delimits a region or looks
for the place in addition, changes the original import
product to domestically produce and supply. 3, through
the property reorganization, the annexation, causes the
main body to be capable, assists divergence and the
attached department, expands and strengthens technical
equip and the working conditions that produce lead
product or the new development product, improves the
competitive ability; 4, many enterprises have to
diverge, to produce other products that have the market
demand or provide service for the society,
simultaneously carries on the employment structure
adjustment. □Entering WTO is a significant
transformation in our country economical domain, may
bring some new situations and questions. Above is just a
forecast according to the situation at present grasps.
Because of the policy level limits, the situations can
not be extremely comprehensive, the conclusions and
countermeasures may not suit every enterprise, also may
not entirely accurate, only is a beginning of research,
which offers a decision-making reference for leaders of
fan profession.
Middle and small size
ventilator for general use
1 . Introduction
In
recent years, the small fan with the work wheel diameter
to be smaller than the 200mm has been widespread used in
the solution of modern technology topic day by day. In
the limit space create microclimate, wireless electric
appliance cooling, the facile filter maintenance as well
as the small air conditioning equipment; all must use
the small ventilator.
In recent years ,the
development of our country electrical appliances
profession is swift, more and more small fan are needed,
the energy conservation and the low noise are inevitable
request, therefore, the high performance small fan is
one of competitive ability essential conditions in the
electrical appliances. However, in our country, the
research to large-scale fan is more universal, very rare
to the small fan, more difficult to find the research of
all kinds of small fans. In our country, many small fan
factories engaged in the small fan production in without
the test platform and Precision work equipment, lead to
the very low efficiency, the noise is big. From certain
aspects, it has restricted the development of our
country electrical appliances profession. Therefore, it
is necessary to do some research to the factors affect
the small fan efficiency, enhances its performance,
reduces the small air conditioning equipment noise, and
reduces the noise influence to the environment people
live.
2.Small fan characteristics
Compared with the middle and
large-size fan, the small fan efficiency is lower, this
is prominent shortcoming of the small fan. It is well
known, reduces the ventilator size to be able to cause
the number (Reynolds number) to reduce, thus causes the
ventilator performance worsening. At the same time, the
influence of ventilator parameter change not only heart
reducing, but size effect. The so-called size effect
refers to geometry similar is completely destroyed in
the small ventilates manufacture. Through the
dimensionless performance curve analysis to the
industrial used centrifugal fan we can see the influence
of size effect, under the operating situation that
approaches the maximum efficiency, the ventilator
reduces to 1/2 original size, the entire pressure
efficiency will drop 10 - 15% [ 1 ].
The
reasons why small fan efficiency is lower: 1. Reynold's
number is smaller, the flow of gas condition is in the
sub critical area, by the boundary-layer theory, and the
flow loss of this area is bigger. 2. Flow channels
relative roughness are bigger, cause the friction losses
to increase; the gap between leaf blade and wind tunnel
is relative bigger, finally the spillage is bigger.
Moreover, because the influence of electrical machinery
and around structure to the flow of gas increases
relatively, also causes its loss to increase.
In
order to enhance the small fan efficiency, to the small
size centrifugal air fan, may increase the leaf blade
entrance width to reduce the flow loss [ 2 ]. Moreover,
increases the small fan processing precision, selects
the high performance leaf blade material, play a certain
role to enhance its efficiency
The small size fan is small,
takes smaller space, as a result of its application; the
radiation of heat interchanger in the air conditioning
equipment changes from the natural convection to forced
convection, strengthen the heat transfer process,
reduces the material consumption, also enable the entire
equipment efficiency to obtain the enhancement. This is
basic reason why it obtains the widespread application
3.The notices for Small-size
fan’s application in air conditioning equipment
3．1 Fan type choice
The small ventilator,
generally speaking, because the Reynolds number is
comparative big and has unstable flow in air condition
,the air current in the cross flow fan causes the
rubbing effect to reduce, then it still has a
considerable efficiency, but the axis flow fan and the
centrifugal fan efficiency are very low in the
miniaturized situation, only could achieve 10 - 15%in
many cases [ 3 ]. Therefore, from the energy
conservation view, in the air conditioning equipments,
the cross flow fan should be used as far as possible,
the noise standard of which is situated between the axis
to flow between the type and the centrifugal type,
regarding the home electric appliances, the measure of
sacrificing the certain efficiency to reduce the noise
also can be taken.
Because
the cross flow fan has thin and long structure design,
is suitable to be installed in all kinds of air
conditioning equipments or in the smaller volume
refrigeration, like the small cold storage, cold
cabinet, cold exhibition cabinet, cooling fan, home use
air conditioner and so on. Applies the cross flow fan in
these equipment, not only may obtain the even air
current organization conveniently, moreover its drive
electrical machinery may conveniently be installed
outside the air duct, like this may cause the air
conditioning equipment to reduce the cold quantity loss
which created by the electrical machinery gives off
heat. This point is quite important, because this cold
quantity ratio is quite considerable.
3．2 Fan types for choose
When
the size of ventilator reduces to D<0．5m,the
characteristic curve changes to be worse than Reynolds
number which caused by ventilator reduction expected.
This is a result of the size effect function, which is
impossible to guarantee the small external dimensions
ventilator to be completely similar to prototype.
Because at present we cannot estimate the characteristic
curve reduction of the small ventilator through the
computation. When select small ventilates, therefore,
the objective parameter as to be suitable.
3．3 Influence on the fan
performance by the shell
The independent work curve
possesses special meaning， because in different
work condition wheel would be installed in different
equipments. As the friction between wheel and air would
be increased in independent condition, so the power it
needed was larger than the ventilation with shell. The
static pressure is larger than ventilation with shell,
but as the lower static pressure and larger power of
independent wheel, its static pressure efficiency would
be lower than the wheel run in shell. So for air
condition equipment generally adopt ventilation with
shell or to form shell structure for these equipments.
3．4 Noise control system
In air condition system, the
noise resource mainly is ventilation. The ventilation
noise is composed of aerodynamic noise, machinery noise
and electromagnetic noise. Aerodynamic noise is composed
by ?? noise, impinging noise and flow noise. Turbulent
flow noise generated when the inlet air was in the
induction mouth and the impeller, it was related with
the air inlet, front-panel structure and other companion
elements. When the speed of impeller is larger, the flow
noise will increase. Impinging noise is generated when
flow in or out the impeller, it is related with fan
flow, angles of the impeller. When flow was larger, the
best work point deviation would larger the noise.
Rotation noise is also called impeller noise, caused by
the pulsation change when impeller made pressure on the
flow. It is related with the rotation speed, diameter of
impeller. When the speed and diameter is larger, the
noise would be larger.
Machinery noise is cause by
the bearing friction, unright installation of
transmission equipment and the misbalance of rotation
parts. Electromagnetic noise is generated by the
reciprocal effect of alternating force in air clearance.
In the special condition
point curve, when it close the max efficiency, the noise
of ventilation reach the minimum, the air induction side
and eduction side has the lowest noise. So , if the
noise level would be infinite, fan must work in highest
efficiency.
Low noise fans generally have wide but less blades.
Centrifugal fans generally has lower noise than axial
fan.
To sum up, the most effect
method to low the noise of air conditioner is declining
the noise of ventilation. Firstly, adopting high
efficiency and low noise ventilation; secondly, choosing
rational bearing, improve assemble precision and check
the dynamic and static balance to low the machinery
noise.
3．5 Other problems
As the small fans have low
efficiency, and they usually stay in partly load
movement, so fuzzy technology and frequency conversion
velocity modulation are usually used to adjust the speed
of fan, which compensate the disadvantage of low
efficiency but high consumption, but also decrease noise
with no influence o the motor efficiency.
What is more, the flow tube
of small fan is narrow, if any obstacle in it, the flow
field would be harmful influenced, the motor and bracket
equipment would influence fan efficiency. So, outside
set motor could be used to decline this influence and
eliminate the cooling volume waste by the motor heat.
4 . Conclusion and
suggestion
4．1 Adopt large size fans as
possible as you can to enhance the whole performance of
the equipment.
4．2 Improving the fan efficiency
and decreasing the noise is relative. As the generation
of noise consumes power, if the space is allowed, cone
bell pressure expander could be set on the air outlet of
axial fan to decrease flow speed, enhance the sir outlet
pressure and decrease the flow impingement.
4．3 The applied small type fan
cooling air condition factories should closely cooperate
with professional fan companies, in order to integrally
form the air tube and scroll to form rational air
channel, decrease noise, decline resistance, enhance the
fan efficiency, what’s more, it could decrease the
equipment size.
4．4 The efficiency of small fans
is related with the performance of motor, as the motor
power should relatively very large to convey air to the
small fan, and the motor shape would influence the flow
field. So, choosing fine performance motor is very
important to small fans. If the processor craft is
allow, the motor could be make in fluent shape which
could enhance the small fan performance.
Refrigerant
air-condition industry has been established the basic
tasks on the “tenth five-year plan”
The refrigerant
air-condition industry was developed earlier from the
planned economy to market economy in China. Through many
year’s struggle, it has been developed quickly and
fast, and each target has been increased 5-8 times. At
present, the output of freezing air-condition equipment
accounts for more than 10% in the output of the world
and it has become the third biggest producing freezing
air-condition equipment in the world.
The competition is more and
more fierce and science and technology changes quickly.
Facing such situation, the refrigerant air-condition in
our country will stride forward into the new century.
The dominant thought of such field during the “tenth
five-year plan ” should be oriented by the market,
assisting excellence and supporting mightiness,
accelerating the pace of the innovation, optimizing the
structure, improving the creativity of technology and
keeping the spirit of development in persistent,
expeditious and healthy way.
Slowing the basic task of
the whole industry should do the followings: improving
the whole industrial diathesis, and building up the
market competition; optimizing the structure of
production and exploiting the international market
energetically; expediting process of the important
technology controlled by China.
The whole industrial target
is involved in the measurable target in
kinds of centralized air-condition: in five
years, compared with the past 10 years, the development
speed of freezing air-condition is slower. It is
estimated that the rising rate of the main products
output is between 6% and 7% averagely.
The occupancy rate of the
domestic products will be improved from 80%～85% to 90%～95%. The import quantity of the products takes on
descendent tendency year after year. Improving the grade
of the products gradually and increasingly strengthening
the market competition throughout the world is more and
more important.
Analysis
report on electric fan industry development TOP
Ⅰ、Retrospect on the electric
fan industry development
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