Available online at www.sciencedirect.com
ScienceDirect Procedia Engineering 121 (2015) 2132 – 2140
9th International Symposium on Heating, Ventilation and Air Conditioning (ISHVAC) and the 3rd International Conference on Building Energy and Environment (COBEE)
Experimental Investigations on Thermal Performance of a New Floor Heating Device Yu Wanga, *, Zhigang Zhanga, Falong Hea and Xueli Liub b
a School of Energy and Safety Engineering, Tianjin Chengjian University, Tianjin 300384, China Tianjin Youlin Honglian Energy Science and Technology Development Co Ltd, Tianjin 300384, China
Abstract
Thermal performance experiments were carried on a new floor heating device in a thermal environmental chamber in order to provide design reference for engineering application. The new floor heating device can achieve heating demand with lower heat medium water temperature when compared with traditional floor radiant heating coil pipe. The device can combined with low grade thermal energy utilization system for high efficient heating. © 2015 2015The TheAuthors. Authors. Published by Elsevier Ltd.is an open access article under the CC BY-NC-ND license © Published by Elsevier Ltd. This (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the organizing committee of ISHVACCOBEE 2015. Peer-review under responsibility of the organizing committee of ISHVAC-COBEE 2015 Keywords: Floor Heating, Thermal performance, Heat-transfer capability
1. Introduction Low temperature floor radiant heating mode is superior to traditional radiator heating mode on improving thermal comfort and energy-saving operation.[1-3] Some new terminal heating device emerged when heat pump combined with floor heating became an important alternative scheme for heating in hot summer and cold winter area or cold area [4-7] . In this paper, thermal performance test were carried on a new floor heating device ( as shown in Fig. 1) in order to provide design reference for engineering application.
* Corresponding author. Tel.: 022-23085277 E-mail address:
[email protected]
1877-7058 © 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license
(http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the organizing committee of ISHVAC-COBEE 2015
doi:10.1016/j.proeng.2015.09.084
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Fig. 1. New type floor heating device
2. Description of the laboratory and experimental method The laboratory for thermal performance tests of the new floor heating device consists of heat medium water supply system, thermal environment chamber and cooled air supply system, as shown in Fig. 2. Tested terminal device such as the new floor heating device is located in thermal environment chamber where can be air-conditioned by cooled air supply system and maintain desired indoor temperature. Cooled air sent into the air jacket from air handling unit meets heat-transfer by the tested terminal device under desired experimental condition.
Fig. 2. Schema of the laboratory for thermal performance test
The inlet heat medium water has access to terminal device through high position water tank. The outlet water from terminal device returns to low position water tank through flow rate measurement device with float flowmeter employed for flow rate check and with electronic scale employed for accurate mass flow rate measurement. The purpose of bypass between high position water tank and low position water tank through three-way pipe connecting inlet pipe is to return excess of the fluid back so as to remain equal to the flow rate of the water when the water
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which come form high position water tank has a higher flow rate than required. The heat medium water temperature is obtained by means of electric resistances heater in low position water tank for rough adjustment and by means of electric resistances heater in high position water tank for accurate regulation. The indoor air temperatures of thermal environment chamber were measured by using PT1000 sensors, which are located vertically 0cm, 5cm, 50cm, 75cm, and 50cm, 5cm, 0cm to ceiling above the floor at the center position (measure point 3 to 9 in Fig. 3) and placed vertically 75cm, 150cm on the line with each1m distance to the adjacent walls (measure point 10 to17 in Fig. 3). In this way, a more uniform and accurate temperature distribution was achieved with the measurements taken. The temperature of each unheated surfaces were measured from the center of the walls by PT1000 sensors (measure point 18 to21 in Fig. 3). The surface temperature for heated floor which located by new device were detected by the average value of 16 PT1000 sensors with uniform layout on the replaceable layer surface (as shown in Fig. 4). All above temperature sensors (PT1000) were calibrated and their accuracy was equal to 0.1 ć. All the measured values by the use of the calibrated sensors were archived with the time interval which is equal to 1 min. The heat transfer quality was estimated after thermal environment chamber reached a steady state which means that the analyzed device in a steady state was characterized by physical properties were unchanging in time.
Fig. 3. Temperature sensors location in the thermal environment chamber
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Fig. 4. Temperature sensors location on the replaceable layer of the tested device
The experimental program consist in supplying the new floor heating device with heat medium water, which temperature values were set at 30ć, 35ć and 40ć. Experimental investigation were conducted on the new floor heating device with 3 different component assembly method (as shown in Fig. 5): (a) single component series with 12 channels flow path; (b) double component series with 24 channels flow path; (c) triple component series with 36 channels flow path.
(a) 12 channels
(b) 24 channels
(c)36 channels
Fig. 5. Three different flow path of the new floor heating device
The total heat transfer quality between the new floor heating device and thermal environment chamber was calculated via Eq.(1) and Eq.(2).
Q
mc p (tsu tre ) A
(1)
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m
M
(2)
W
Where, Q—heat transfer quality, W/m2; m—mass flow rate, kg/s cp— the specific heat value of water, kJ/kg·ć tsu—supply water temperature, ć tre—return water temperature, ć A—component area, m2 M—heat medium water weight, kg τ— time for weight scale, s 3. Results and discussions Calculated results about start-up period of the tested device are shown in Fig. 6. Heat-transfer capability of the new floor heating device increased in 3 hours after the system starts up, and then became stable. The heating capability of the new device increases when the supply water temperature increases as is expected, as shown in Fig. 7. Supply water temperature has significant effect on heat-transfer quality of the new floor heating device. Heattransfer quality ranges 30 to35 W/m2 when 30ć inlet water is accessed; Heat-transfer quality ranges 45 to 55 W/m2 when 35ć inlet water is accessed; Heat-transfer quality ranges 65 to 80 W/m2 when 40ć inlet water is accessed Fig. 8 shows the heating performance of the new floor heating device as a function of the temperature difference (ts-tref) between surface temperature of the tested device and reference position (75cm above the floor on the center line) temperature. Each experimental investigation of the data follows a different but similar trend line. The proposed equation for heating quality (qtotal) about the new device employed on floor heating depending on assembly method and flow temperatures in the study will be as follow equations:
qtotal
13.655(ts tref ) , 12channels
(3)
qtotal
12.485(ts tref ) , 24channels
(4)
qtotal
12.694(ts tref ) , 36 channels
(5)
2
Heat-transfer quality (W/m )
90 80 40ć
70
35ć 30ć
60 50 40 30 20 60
90
120
150
180
(a) 12 channels
210
240
270
Time(min)
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2
Heat-transfer quality(W/m )
30ć 35ć 40ć
100
130
160
190
220
250
280
Time(min)
(b)24 channels
2
Heat-transfer quality (W/m )
70.0 60.0
30ć
50.0
40ć
35ć
40.0 30.0 20.0 140
160
180
200
220
240
Time(min)
(c)36 channels
2
Heat-transfer quality (W/m)
Fig. 6. Heat-transfer performance of the new floor heating device after start-up
90 80 70 60
ć ć ć
50 40 30 20 25
30
35
40 45 supply water temperature˄ć˅
(a) 12 channels
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2
Heat-transfer quality (W/m)
80 70 60
ć ć ć
50 40 30 20 25
30
35 40 45 supply water temperature˄ć˅ (b)24 channels
2
Heat-transfer quality(W/m)
80 70 60
ć ć ć
50 40 30 20 25
30
35
40 45 supply water temperature˄ć˅
(c)36 channels Fig. 7. Heat-transfer capability of the tested device affected by supply water temperature
2
heat-transfer quality(W/m )
85 75 65 55 45
36 channels 24 channels 12 channels 36 channels (y=12.694x) 24 channels (y=12.485x) 12 channels (y=13.655x)
35 25 15 1.0
2.0
3.0
4.0
5.0
6.0
Fig. 8. Heating performance of the new floor heating device
7.0
ts-tref (ć)
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Table 1 lists thermal performance of the tested device with different flow path. When the average temperature of heat medium water in the new floor heating device is between27.5ć and 28.9ć, the heating index can reach 34.9W/m2 with space temperature in the environmental chamber maintaining at 23ć. When the average temperature of heat medium water in the new floor heating device is between31.0ć and 33.1ć, the heating index can reach 53.7W/m2 with space temperature in the environmental chamber maintaining at 23.5ć. When the average temperature of heat medium water in the new floor heating device is between35.3ć and 37.4ć, the heating index can reach 80.6W/m2with space temperature in the environmental chamber maintaining at 24.1ć. Table 2 quoted from Technical specification for floor radiant heating (JGJ-142-2004) lists thermal performance of traditional device. Compared with Table 1, it can be seen that the new floor heating device with the average temperature of heat medium at 31.0~33.1ć can reach the heat radiation level as PB coil with the average temperature of heat medium at 35ć.The new floor heating device with the average temperature of heat medium ranging from 35.3 to 37.4ć has the same heating effect as PB coil with the average temperature of heat medium at 40ć. Table 1. Thermal performance of the tested device with different flow path Aver. Temp.
12 channels Chamber Temp.ć
ć
27.5 ~28.9 31.0 ~33.1 35.3 ~37.4
24 channels
Heat radiation (W/m2)
36 channels
Chamber Temp.ć
Heat radiation 2
(W/m )
Chamber Temp.ć
Heat radiation (W/m2)
23
34.9
21.7
34.0
20
30.3
23.1
34.8
21.9
32.4
20.2
29.2
23.3
52.8
23.1
52.9
22.5
47.5
23.5
53.7
23.3
53.4
22.8
46.8
24.1
80.6
25.1
72.6
22.3
68.7
24.3
80.3
25.3
70.8
22.7
66.3
Table 2. Thermal performance of traditional device (PB coil floor heating with plastic surface layer) Heat radiation (W/m2) Aver. Temp. (ć)
35
40
Room Temp. (ć)
Pipe Space
Pipe Space
Pipe Space
100mm
150mm
200mm
20
66.1
62.0
58.0
22
58.0
54.5
51.0
24
50.1
47.1
44.1
20
88.3
82.8
77.2
22
80.1
75.1
70.1
24
71.9
67.5
63.0
4. Conclusions Based upon measurements and comparisons, the following conclusions are drawn: (1) The floor heating system employ the new device can achieve thermal comfort at lower supply water temperature when compared with traditional technology equipment for floor heating.
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(2) Heat radiation of the new device ranges from 46~54 W/m2 when supply water temperature ranges from 30~35ć. It is suitable for the new device to combine with low grade heat source such as solar collector or heat pump for building heating in north China with cold climate. References [1] G. Zhou, J. He, Thermal performance of a radiant floor heating system with different heat storage materials and heating pipes. Appl. Energ. 138 (2015) 648-660. [2] L. Zhang, X. H. Liu, Y. Jiang, Simplified calculation for cooling/heating capacity, surface temperature distribution of radiant floor. Energ. Buildings. 55 (2012), 397-404. [3] J. Seo, J. Jeon, J.H. Lee, S. Kim, Thermal performance analysis according to wood flooring structure for energy conservation in radiant floor heating systems. Energ. Buildings. 43 (2011), 2039-2042. [] K. Zhao, X.H. Liu, Y. Jiang, Dynamic performance of water-based radiant floors during start-up and high-intensity solar radiation. Sol. Energy. 101 (2014) 232-244. [] J.M.C. López, F.F. Hernández, F.D. Munoz, A.C. Andrés, The optimization of the operation of a solar desiccant air handling unit coupled with a radiant floor. Energ. Buildings. 62 (2013) 427-435. [] D./. Zhang, N. Cai, Z.J. Wang, Experimental and numerical analysis of lightweight radiant floor heating system. Energ. Buildings. 61 (2013) 260-266. [] C. Verhelst, F. Logist, J.V. Impe, L. Helsen, Study of the optimal control problem formulation for modulating air-to-water heat pumps connected to a residential floor heating system. Energ. Buildings. 45 (2012) 43-53.
