Radiant Floor for Heating and Cooling - New Type of Displacement Ventilation Air-conditioning System...

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Radiant floor for heating and cooling - new typeof displacement ventilation air-conditioningsystem in the Beijing area Feasibility Analysis

Abstract: The project for the Beijing Construction Engineering College of heat, Gas Su

pply, Ventilation and Air Conditioning Engineering Key Laboratory of research: radiatio

n for heating and cooling - new type of displacement ventilation air-conditioning system

in the Beijing area of the feasibility study. This paper describes the layout of the experi

ment station system, the form describes how to solve the floor radiant cooling for sum

mer air-conditioning condensation when the people's worries, pointing out that the intr

oduction of a displacement ventilation system, not only through the cold air into the dry

In the cold floor of the lake formed on the surface layer of the air and reduce the cold s

urface of the floor of the dew-point temperature, increase its cooling capacity, while its

elf can take a certain amount of cooling load. An analysis of the system is used for hea

ting and cooling of the feasibility of the Beijing area, and the winter operation of the sy

stem has done a preliminary test and analysis, and practice proved that the system is

used to good effect to use in winter heating, saving energy consumption, indoor comfo

rt moreWell.

Key words: radiation for heating and cooling - temperature of the feasibility of displace

ment ventilation

1 Introduction

Low temperature radiant heating, is a use within the building floor, walls, top or other s

urface heating systems to radiant floor heating is most commonly used. Because of its

surface area of radiation and indoor use basically the same size, so you can evenly to

the entire heating, so room temperature uniformity. In our northern regions, low-temper

ature hot water radiant floor heating systems in their health conditions in the high, com

fortable, good temperature uniformity, ease of use of natural energy and energy savin

g advantages of cold and heat source such as widely used. The same set of systems s

uch as can be used for both summer cooling will reduce the initial investment in equip

ment to increase their efficiency, while the floor for the warm and cold - displacement v

entilation, air-conditioning system in the complex energy-saving, comfort, indoor harmf

ul gas emissions to improve indoor air quality, of other heating and air conditioning sys

tems can not match advantage. Floor cooling with displacement ventilation combined c

ondensation problems can be solved, but in different regions, different weather conditi

ons when using the equipment may have a greater difference between the system mus

t be locally studied. To this end, we have built in Beijing Institute of Technology campu

s for the construction of a radiation heating - displacement ventilation system, new air-

conditioned laboratory bench, to be further study of characteristics of the system and c

arry out experimental analysis, so that the floor at the same time cooling technology an

d equipment to further mature, to promote the use of.

2 Experimental program

2.1 Experimental Conditions

Experimental rooms are located outside the Beijing Construction Engineering College,

Beijing Xizhimen a two-story school's ground floor, indoor use of an area of 32 �O, co

nstruction area is about 35 �O. Experimental room walls on both sides something to 3

7 bricks; north and south walls of 24 brick wall, next door to not heating the room. Singl

e-layer glass windows, steel window. After load calculation, to be experimental room, th

e total cooling load of 114W / �O, wet load of 0.956Kg / h, the latent heat load of 610

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chinese Version | English

13/10/2010 Radiant floor for heating and cooling -…

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e total cooling load of 114W / �O, wet load of 0.956Kg / h, the latent heat load of 610

W. Cold-shoulder the load all of the floor of the cooling load for the obvious, plans for t

he 42W / �O, fan coil cooling load required to undertake for the 2.3kW, in which the la

tent heat load of 610W.

2.2 Floor Pipe Layout

The laying of pipe at the end of the first high-performance thermal insulation materials

(using 40 mm thick polystyrene foil increases, density �� 20 kg / m3), play a one-way

insulation and heat insulation effect. Pipe using cross-linked polyethylene pipe (PEX) p

ipe, diameter of DN16, tube spacing 100 mm, double-loop layout to minimize the unifor

m surface temperature, the circuits are basically the same tube length and a length of

90m or so in order to drag balance, amount of water evenly. The laying of sub-four-loo

p (see Figure 1), A-loop: at the side of the room, spacing 200 mm; B Loop: A loop in th

e middle of the formation of sets of pitch 100 mm. C-loop: A loop with, at the other side

of the room; D-loop: Same as B circuit, set in the middle of the formation of C spacing

100 mm; A, C loop between the loop and the outer wall of the room also maintained be

tween the 100mm spacing, each for a loop through the backwater valve on the manifol

d to switch. Floor tube filled with layers of 30 mm crushed stone concrete, expansion jo

ints at intervals of 5m square set, leveling layer of about 20 mm, surface decoration m

aterials, thermal conductivity of a strong selection of floor tiles, structural layer thicknes

s of about 70 ~ 80 mm.

2.3 The winter and summer air-conditioning treatment options

Use of air-source heat pump system, hot and cold as the source, because of its ease o

f use of natural energy resources, the system thermal efficiency is greater than 1, with

energy-saving advantages, rational use, reduce energy consumption and operating co

sts. The system flow chart shown in Figure 2, summer cooling, dehumidifying operation

, the cut-off valve A closed, cut-off valve B opens, from the cold water first passes thro

ugh the fan coil units, the temperature rise after the backwater compared with the cold

floor mixed, as the cold water supply in the floor. As the wet load all be borne by the fa

n coil, fan coil inlet temperature requirements so low, about 7 �� or so, if one is consi

dering a heating rate of 5 ��, then the fan coil of the water temperature around 12

��, the If the floor control directly for the temperature, the temperature is still too low,

significantly lower than the dew point temperature of the summer in Beijing, will cause t

he cold floor surface condensation. The literature recommended floor cooling water te

mperature is 18 ~ 20 ��, so the water fan coil should be mixed with the cold floor of t

he backwater and then supply the cold floor, the floor pipes by setting the water tempe

rature to control the amount of water mixed with three-way valve. Direct water to the flo

or in winter to the tube, this time cut-off valve B closed, A cut-off valve to open. Runnin

g does not require mixing with water in winter when the two pumps shut down.

Because of financial constraints, the project failed to purchase new equipment, accordi

ng to current needs, using existing equipment, a larger margin. Experiment with the he

at pump units with good air-conditioner plant in Suzhou Taiwan produced air-cooled he

at pump units, rated heat capacity 19.5kW, rated cooling capacity of 16.3kW, comes wi

th pump rated flow 6.3m3 / h, Head 20m, power 0.6 kW; Heat Pump total input power of

7.5 kW. Fan coil units are used in artificial environments Tsinghua Tongfang Co., Ltd.

product of horizontal installation of fan coil units, model: FP-6.3, air flow 671m3 / h, coo

ling capacity 3500W, Thermal 5763W, input power 32W.

3 for the radiant floor heating - a new displacement ventilation of the feasibility and sup

eriority of the air-conditioning systems

Is well known for its low temperature radiant floor heating means comfort, energy efficie

ncy, and good sanitary conditions, have been rapidly across the country to promote thi

s will not repeat them; while the same set of systems, such as can be used for both su

mmer cooling will reduce the equipment initial investment, to enhance its efficiency, an

d therefore has been more and more attention. However, due to fears that the floor co

ndensation, thermal comfort issues, as well as the cold floor of the cooling capacity, en

abling the application of floor cooling under certain restrictions, such as radiant floor h

eating is not as rapid popularity.

Indeed, when the cold water temperature of the lower floor or indoor humidity, the cold

surface of the floor may be condensation, limiting the cold floor of the cooling capacity

can not meet the comfort requirements. However, if combined with displacement ventila

tion system can solve the above problems. By displacement ventilation system into the

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air through the cooling dehumidification, because of its high density and deposited on t

he cold surface of the floor, forming a layer of air lake, thereby preventing heat and m

oisture of air in direct contact with the cold floor to reduce the cold surface of the floor

of the dew point temperature, can guarantee the water temperature low enough to imp

rove the cooling capacity of the cold floor. Meanwhile, the displacement ventilation syst

em itself can also bear some of the cooling load, and the combination of radiant floor c

ooling system, you can reach a higher comfort requirements. Furthermore, for people

concerned about thermal comfort issues, studies have shown that the floor temperatur

e was controlled at 18 ~ 20 �� within the framework of the summer does not produce

the feeling of cold feet with the combination of displacement ventilation systems, you c

an take All indoor cooling load.

Reposted elsewhere in the paper for free download http://www.hi138.com

4 Winter operation

4.1 Heat Pump Operating Parameters

As the structures laboratory bench and other reasons, the test of time mainly in late Fe

bruary 2004 and the beginning of March. Although the weather has been warmer, but

still feel that chill of early spring, indoor and outdoor temperature and humidity produc

ed by Tsinghua Tongfang temperature and humidity of self-recording instrument collec

tion, automatically recorded once every half an hour. Calorimeter cooling system is inst

alled, flow meter, heat pump unit installed in a separate meter, used for measurement,

statistics and operational control. Heat Pump Thermal power consumption and heat me

ters by meters and measurement, to show that, due to excessive margin unit, using an

effective volume of 300 liters of storage water tank to adjust in order to avoid frequent

compressor start, set the maximum water temperature 45 ��, temperature adjustable

rate raised to 15 ��, the actual operation of Starting and stopping time than about 0.

2:1. To this end, the actual COP group of computers, we should deduct pump power c

onsumption. Testing period, outdoor temperatures most of the time in between 6 ~ 10

��, outdoor minimum temperatures -2 ��, the general minimum temperature is bet

ween 4 ~ 7 ��. After repeated measurements, in continuous operation for 50 hours,

reaching a steady state, the measured average power consumption unit is about 1.04k

W / h, less pump power consumption of 0.6kW / h, the power consumption of 0.44kW /

h; the average heat capacity of about 1.53kW / h, calculated COP value of about 3.5.

4.2 The room temperature experimental results

In order to study for the radiant floor heating - the use of displacement ventilation resul

ts, the laboratory temperature and inner surface of the envelope structure were measu

red at room temperature. Envelope inner surface temperature measured by thermal im

aging devices, taking the average of multi-point measurement; room temperature with

Tsinghua Tongfang produced temperature and humidity measured by self-recording in

strument, the average of several tests in Table 1.

Floor temperature, surface temperature inside the building envelope and indoor air te

mperature gauge 2



As can be seen in the test floor radiant system, with the surface temperature, indoor s

urface temperature is higher, an area weighted average temperature close to room te

mperature. In addition, because the body's comfort is radiation and convection combin

ed effect of two kinds of heat transfer can be used to indicate the role of the temperatu

re. According to the literature introduced in the indoor wind speed is very low, the role

of the temperature structure of the surface of the envelope can be considered equival

ent to the average temperature and indoor air temperature, on average, that is, in floo

r radiant heating system, radiation and convection heat transfer in two ways comfort on

the human body has the same effect.

5 Preliminary Conclusions

(1) radiation for the heating and cooling - a new air conditioning system for displaceme

nt ventilation in Beijing winter heating, fully able to meet demand at room temperature.

(2) As the heat pump's own energy efficiency, than the use of electric boilers and other

equipment to save energy and operating expenses on the obvious advantages.

(3) The floor cooling system combined with displacement ventilation by displacement v

entilation system to take over all the latent cooling load and the indoor part of the signi

ficant cooling load, cold floors bear the significant cooling load, fully meet the summer

cooling requirements.



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(4) The project unit margin due to too much, the pump with the rated flow and head is t

oo large, causing the pump energy is too large, wasting some energy. Actual use, the

choice of units do not have to keep a larger margin.

References:

[1] BWOlesen. Possibilities and Limitations of Radiant Floor Cooling. ASHRAE Transac

tion 103 (1): 42 ~ 48 (1997, Part.1)

[2] Wang Kai, air-source heat pump for residential radiant floor heating experimental st

udy. HVAC, 2003 (1): 56 ~ 58

[3] Prince or referred. Radiant floor cooling and air-source heat pump geothermal feasi

bility research and analysis. The national heat pump and air conditioning technology e

xchanges Papers, 2001,258 ~ 265

[4] LI Xian, the prince referred. Floor cooling displacement ventilation air-conditioning s

ystem in residential building complex in the application of electrical and intelligent buildi

ngs, 2002.11:62 ~ 65

[5] Huang also Yun, Zhang Ling, Chen Guangming, radiant floor cooling dehumidificati

on issues to explore, HVAC 2003 (3): 47 ~ 51

[6] Zhao Rongyi, eds. Air-conditioning ��M��. Beijing: China Building Industry Pres

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Radiant Floor for Heating and Cooling - New Type of Displacement Ventilation Air-conditioning System...

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