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구들  |  김준봉  |  사진  |    |  閲?sop=and  |  â€¦Ã¬Â  2017년 12월 18일 월요일
논문투고Presentation Paper论文投稿 > 중문논문/中文论文
   
  Evaluation and Application of the New Ondol System for Warmer & Cooler Zone
  글쓴이 : 운아     날짜 : 10-02-12 21:52     조회 : 9938    

Evaluation and Application of the New Ondol System for Warmer & Cooler Zone
in Apartment Houses


Dongwoo Cho1, Kihyung Yu2, Jungyeon Yu3

1 Director, Building & Urban Environment Research Division, Korea Institute of Construction Technology
2 Senior Researcher, Building & Urban Environment Research Division, Korea Institute of Construction Technology
3 Researcher, Building & Urban Environment Research Division, Korea Institute of Construction Technology

……………………………………………………………………………………………………………………………
Abstract
The purpose of this study is to develope the new floor heating system with an improved performance than an existed  floor heating system for apartment houses. The Ondol systems for warmer & cooler zone developed in this study were applied to an experimental apartment house and a mock-up room. The field measurements for this system were executed in winter climates. As a result of field measurement, when the heating load differences between perimeter zone and interior zone are increased, the separately controled Ondol system divided in the warmer zone and cooler zone can be used as the new Ondol system with a capability for suppling proper heating energy for each zone. The user can have the freedom for changing warmer zone and cooler zone and controlling each indoor temperature according to their needs.
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Keywords : apartment houses, floor heating system, Ondol systems for warmer & cooler zone, field measurement
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1. Introduction

1.1 Purpose of the Study

Ondol is a typical radiant floor heating system in Korea and it means conventional Ondol to heat under the floor structure by putting hot air. It had been recognized as a comfortable heating system to create "warm floor and cool room temperature", however, hot-water floor heating system was settled down as general type, which lays hot-water heating pipes under the floor by improving heat efficiency of Ondol and modernizing the heating system recently through the changes in several stages followed by the change of  life style and heat source system.
Current floor heating systems had been applied to most apartment houses in the form of laying and finishing hot-water heating pipes to mortar layer on the upper side after completing insulation and horizontal construction of building slab, but the phenomenon that room temperature was excessively rosen for keeping warm floor and that floor temperature was too low for keeping cool room temperature since the deviation between floor temperature and room temperature was decreased due to the change of heating load followed by high performance insulation and airtightness of buildings.
It is judged that such problem occurred since the improvement of heating techniques or the adoption of appropriate operating technique followed by the change of thermal performance of buildings rather than the problem of floor heating system itself, and it would be resolved by the improvement of radiant floor heating system.
In this study, therefore, the new Ondol system for warmer and cooler zone is presented, the distribution of floor temperature and room temperature of the warmer and cooler zones is measured for the mock-up room and an experimental apartment house, and  the result is analyzed by comparison. The capability of this system as a floor heating system for apartment houses is to be evaluated through the analysis.



2. Ondol System for Warmer and Cooler Zone

To compose Ondol system for warmer and cooler zone, the amount of heating in the warmer and cooler zones should be supplied deferentially, for the method, the methods to differ the cross section structure of Ondol in the upper and lower side, adjust the interval of heating piping, or control the supplying flow quantity can be presented.
However, the method available for real introduction is to apply the  composition of piping and the control technique. 
First, the method to compose the warmer and cooler zoning through the adjustment of piping interval in a pipe line is shown in the Figure 1. Currently, the installation interval of pipe forms the piping network with the same piping interval by 200mm or 250mm when a room is selected. But much heating load is taken at window side zone and less heating load is taken at the indoor space even in the same space. Therefore, floor surface temperature is highly formed and the floor surface temperature of indoor side zone is lowly formed by installing piping interval narrowly at window side zone in response to the load near window side zone that has much heating load. Such method can divide the space of the warmer and cooler zones by adjusting piping interval using a pipe as shown in Figure 2 (a).
The differentiation of floor surface temperature can be planned by supplying hot water to window side space and then  receiving it in the indoor space. DIN 4725 regulates that floor surface temperature of inhabitation space cannot exceed 29℃ but allows up to  35℃ for floor surface temperature with the method to apply different piping interval since much heating load is consumed at window side.
Next, the method to compose the warmer and cooler zones in parallel with piping interval adjustment and 2-pipe zoning is shown in Figure 2 (b): This is the system to compose the warmer and cooler zones by dividing a space into 2 heating zone and composing 2 piping network, and arranging the piping interval of the warmer zone narrowly and that of the cooler zone widely. The deviation of floor surface temperature between the warmer and cooler zones can be much more generated rather than the case of composing single-zone piping.


Figure 1. The Piping Composition of The Upper and Low Side zones in various Types


    (a) Single-zoning Piping          (b) Double-zoning Piping

Figure 2. The Distribution Characteristics of Floor Surface Temperature in the upper and lower side zoning composition in single-zoning piping (a) and double-zoning piping (b) (REHAU, 2007)


  (a) Mock-up Room 


 











        (b) Experimental Apartment House

Figure 3. Test Buildings for Ondol system for warmer and cooler zone
 3. Thermal Performance of Ondol System for warmer and cooler zone

3.1 Summary of Experiment

This research has the final intention for usefulness by developing comfortable Ondol system available for response to the characteristic of  inhabitants to satisfy the objective performance. It also is to develop Ondol system considering the characteristics of district heating to supply hot water in low temperature and to develop Ondol system available for response to load variation such as balcony extension.
Therefore, we executed experiments in two buildings as shown in Figure 3 to attain the warmer and cooler zone for more perfected form..

3.1.1 Application of Ondol System for warmer and cooler zone in Mock-up Room
First, to execute the test for thermal performance and control result about the composition of the warmer and cooler zone by the piping interval adjustment as shown in Table 1. The mock-up room in 22㎡ scale, which was made in the form of living room in an apartment, was constructed for testing at the first floor of laboratory building in KICT. As shown in Figure 4, the piping interval was made by 150㎜ in the warmer zone located indoor space, and by 300㎜, two times of the warmer zone, in the cooler zone located at window side. Using plastic pipe  with 20㎜ in diameter, the piping network with radiant type was made in the warmer zone and the piping network with parallel type was made in the cooler zone. Finally, finishing mortar with the thickness of 40㎜ was used for the construction.
At the mock-up room, the floor surface temperature was measured by attaching thermocouple in the vertical and horizontal direction with the interval in 60㎝ on the floor surface of the warmer and cooler zones to measure thermal performance as shown in Figure 5. Indoor temperature was measured by installing thermocouple at the vertical hight of 50㎝, 100㎝, 150㎝ respectively in the center of the warmer and cooler side, and globe thermometer was installed at the vertical height of 80㎝ to measure radiant temperature. Thermocouple was also installed near piping materials and hot-water pipes in hot-water distributor when constructing. Thermostat was installed in the center of the room as shown in Figure 8 for heating and room temperature in the experiment set by 24℃.
 
Item
Details
Testing Place
Mock-up room at the first floor in a experimental house
Testing Condition
Composition of the warmer and cooler zone through the piping interval adjustment in a pipe in the living room of an apartment
Testing Subject
Evaluation of the thermal performance of the warmer and cooler zone
Measurement Elements
-Room temperature per vertical height of the warmer and cooler zone
-Floor surface temperature of the warmer and cooler zone
-Radiant temperature of the warmer and cooler zone
-Outdoor air temperature
Setting Conditions
Space Composition
The cooler zone(balcony); the warmer zone(indoor)
Piping Composition
The cooler zone(piping interval: 300㎜)
The warmer zone(piping interval: 150㎜) single-zoning piping
Control Method
Room temperature control (set temperature: 24℃)
Table 1. Summary of the Testing in Mock-up Room









 









150mm
300mm
          (a) Floor plan              (b) Piping Composition

Figure 4, Piping Composition of Mock-up Room installing the warmer and cooler zone(Single-zoning Piping)










 




Measurement  Point of the Upper side zone
Measurement 
Point of the Lower side zone






Figure 5. Measurement point of room temperature and floor temperature for measuring thermal performance of the warmer and cooler zone(Mock-up Room)













Thermostat (Room Temperature Control)
Figure 6. Indoor Thermostat for Room Temperature Control (Mock-up Room)














3.1.2 Application of Ondol System for the warmer and cooler zone in the Experimental Apartment House
Next, to execute the tests for thermal performance and control method in the case of composing the warmer and cooler zones by applying 2 pipelines and the piping interval adjustment as  the same time as shown in Table 2.
The test room was made at the second floor of experimental apartment house of S construction company to observe the situation of the living room in an apartment.
As shown in Figure 7As, it was sectioned off by the warmer zone and cooler zone with 2 spaces, and the mock-up room was correspondingly applied to the living room space for the household applying enlarged balcony. The interval of piping for the warmer zone at window side space was made by 100㎜ and 150㎜, that of the cooler zone at indoor side space was made by 200㎜ and 300㎜. Using plastic pipe with 20㎜ in external diameter, the piping network in radiant type was made in the warmer zone and the piping network in parallel type was made in the cooler zone. Finally, finishing mortar with the thickness of 40㎜ was used for the construction  and Ondol floor material was used for last finishing.
In addition, the experiment was executed in the state of opening external balcony window to implement balcony enlargement, and heat loss to the lower space of Ondol was interrupted by heating adjacent room at first floor in the laboratory. At experimental apartment house, the floor surface temperature was measured by attaching thermocouple in the vertical and horizontal direction with the interval in 60㎝ on the floor surface of the warmer and cooler zone to measure thermal performance as shown in Figure 8.
Indoor air temperature was measured by installing thermocouple at the vertical hight of 50㎝, 100㎝, 150㎝ respectively in the room space of the center of the warmer and cooler zones. Thermocouple was also installed near piping materials and in hot-water piping of manifold when constructing. As shown in Figure 9, the thermostat for controlling of the warmer zone was installed at window side space, and another thermostat was installed at indoor side space near to kitchen. 



Item
Details
Testing Place
Experimental apartment house at the second floor of laboratory building in an apartment
Testing Condition
Composition of the warmer and cooler  zone through the piping interval adjustment in two pipes in the living room of an apartment to which balcony enlargement is applied
Testing Subject
Evaluation of the thermal performance of the warmer and cooler zone in room temperature control
Measurement Elements
-Room temperature per vertical height of the warmer zone and cooler zone
-Floor surface temperature of the warmer and cooler zones
- Radiant temperature of the warmer and cooler zones
-Outdoor air temperature
Setting Conditions
Space Composition
The cooler zone (indoor)/warmer zone (balcony)
Piping Composition
The cooler zone (piping interval: 200~300㎜) /
The warmer zone (piping interval: 100~150㎜)
double-zoning Piping
Control Method
Room Temperature Control (Set temperature 24℃)
Table 2. Summary of the Test in Experimental Apartment House




















150mm
100mm
300mm
200mm
          (a) Floor plan            (b) Piping Composition

Figure 7. Floor plan and piping composition of experimental apartment house installing the warmer and cooler zone (double-zone piping)

















the lower side
of Ondol system
the lower side
of Ondol system
Figure 8. Measurement point of room temperature and floor surface temperature for measuring thermal performance of the warmer and cooler zone in the experimental apartment house
















(a) The cooler zone
  (b) The warmer zone
Figure 9. Indoor thermostat for room temperature control in the experimental apartment house


















3.2 The Analysis of the Measurement Result of the Warmer and Cooler Zone

3.2.1  The Result of Infrared Ray Photograph
To analyze the distribution of the floor surface temperature at mock-up room in which the Ondol system for the warmer and cooler zone was implemented through the piping interval adjustment in a pipe in detail, we reviewed the distribution of the floor temperature using infrared camera prior to this testing. In the case of controlling room temperature by setting room temperature with 24℃, the highest floor surface temperature showed 28.4℃, and the lowest floor surface temperature showed 24.4℃ in the cooler zone. At that time, it was found that the floor surface temperature in the warmer zone, which  was more dense in its piping interval by two times, was remarkably high. The highest floor surface temperature showed 32.2℃, and the lowest floor surface temperature showed 29.1℃. The warmer zone showed equivalent distribution of the floor temperature deviation around 1K, while the cooler zone showed large difference of deviation by 5K or over.
The mock-up room for the warmer and cooler zone was implemented by applying 2-pipeline network in the experimental apartment. In the case of setting 24℃ for room temperature and controlling room temperature, the floor surface temperature of just upper part of piping in the lower side, composed of the piping interval by 150㎜ as shown in Figure 11, showed 40.0℃ (a in Figure 11), the floor surface temperature in the center of between the pipe and pipe showed 38.6℃ (b in Figure 11), the floor surface temperature of just upper part of piping in the upper side, composed of the piping interval by  300㎜, showed 33.3℃ (c in Figure 11), and the floor surface temperature in the center between the pipe and pipe showed 31.8℃ ( d in Figure 11). Therefore, it was found that the floor surface temperature of the warmer zone, which was more dense in its piping interval by two times, was remarkably high. The deviation of floor surface temperature in the cooler zone and warmer zone both showed equivalent distribution of floor temperature by 1.5K or about.



Figure 10. Distribution of Floor Surface Temperature measured by Infrared Ray Camera (Mock-up Room)



Figure 11. Distribution of Floor Surface Temperature measured by Infrared Ray Camera (Experimental Apartment House)

3.2.2 Distribution of Room Temperature and Floor Surface Temperature

The distribution of room temperature and floor surface temperature is shown in Figure 12, 13.
In the case of mock-up room, in which the warmer and cooler zones were composed through the piping interval adjustment in a pipe, room temperature of the  warmer  zone and cooler zone showed almost similar distribution of room temperature in both space by approx. 23℃ as shown in Figure 12. The floor surface temperature of the cooler  zone (piping interval:  300㎝)was average approx. 28℃, and temperature deviation was approx. ±2.5K, and the floor surface temperature of the warmer zone (piping interval:  150㎝) was average approx. 34℃ and temperature deviation was approx. ±4K. The warmer zone, which had larger radiant quantity at the same area due to the difference from the piping interval, showed higher floor surface temperature by approx. 6K than the cooler zone.
In the case of experimental apartment house, in which the warmer and cooler zones were composed through the piping interval adjustment simultaneously, room temperature of the warmer and cooler zones showed almost similar distribution of room temperature by approx. 24.5℃ in both space modes. The floor surface temperature of the cooler zone (piping interval: 300㎝) was average approx. 29℃, and temperature deviation was approx. ±2.5K, and the floor surface temperature of the warmer zone (piping interval:  150㎝) was average approx. 35℃ and temperature deviation was approx. ±3K. The warmer zone, which had larger radiant quantity at the same area and longer hot-water supply time due to the difference from the piping interval, showed higher floor surface temperature by approx. 6K than the cooler zone. As the warmer and cooler zones were composed by 2 pipes respectively, the floor surface temperature of the warmer and cooler zones  showed the shift followed by each hot-water supply period.
Room temperature and the distribution of hot-water temperature is shown in Figure 14 ,15, in the case that the warmer and cooler zone was composed of 2 pipes, hot-water  supply time of the cooler zone was about 7 hours, that of the warmer zone was about 18 hours showing large difference by about 11 hours between the cooler zone and warmer zone. Hot-water was more supplied to the warmer zone located at window side due to large heating load, and minimum hot-water was suppled to the cooler zone that was hardly affected by outdoor air due to its location at indoor side.

Figure 12. Distribution of indoor air Temperature and Floor Surface Temperature (Mock-up Room)













Figure 13. Distribution of indoor air Temperature and Floor Surface Temperature (Experimental Apartment House)













Figure 14. Distribution of indoor air Temperature and Hot-Water
Temperature (Mock-up Room)













Figure 15. Distribution of indoor air Temperature and Hot-Water Temperature (Experimental Apartment  House)












In the case that the warmer and cooler zones were composed of 1 pipe, however, the floor surface temperature of the warmer and cooler zones showed the shift by the same pattern as shown in Figure 14, and hot-water supply time of the  warmer zone and cooler zone was about 10 hours in the same. Hot-water supply period of the warmer zone and cooler zone was about 3.5 hours so it was found that hot-water was supplied frequently.
The distribution of indoor vertical temperature is shown in Figure 16, 17, and it showed comparatively equivalent distribution of temperature by average 24℃ and the temperature deviation by ±2K as shown in Figure 16. In Figure 17, almost equivalent distribution of room temperature was shown by average approx. 24.5℃ and temperature deviation by approx.  ±1.5K.
The distribution of floor surface temperature at the mock-up room and experimental apartment house is shown in Figure 18, 19 respectively.
In the case of mock-up room, in which no finishing material was applied separately on the finishing mortar, the difference of floor surface temperature between hot water pipes did not largely occur in the warmer zone, but the difference of temperature was very largely showed between the floor surface temperature through which the piping was passed, and the floor surface temperature through which the piping was not passed, in the cooler zone.
In the case of the experimental apartment house in which wooden floor was used for finishing material, however, the difference of floor surface temperature between hot water pipes did not largely occur in the warmer and cooler  zones both; since heat transmission was much made in horizontal direction in wooden floor which had large resistance of heat transmission and radiated heat to the upper part slowly. In the past days, One of the issues was the unbalance of floor surface temperature in the case of the cooler zone. Because the floor surface temperature of part through which the piping was not passed was too low, occupants received unpleasant sense. But the issues can be resolved by applying wooden floor on the above.

3.2.3 Result Analysis and Discussion
In the both of case that the warmer and cooler zones were composed through the piping interval adjustment in single  pipeline network and double pipeline network, room temperature was approx. 24~25℃ both. The floor surface temperature was approx. 28~29℃ in the cooler zone that had the piping interval with 300㎜ and approx. 38~39℃ in the warmer zone that had the piping interval with 150㎜.

Figure 16. Distribution of Vertical indoor air Temperature
(Mock-up Room)












Figure17. Distribution of Vertical indoor air Temperature
(Experimental Apartment House)













Figure 18. Distribution of Floor Surface Temperature of Perimeter Zone and Central Zone (Mock-up Room)













Figure 19. Distribution of Floor Surface Temperature of Perimeter Zone and Central Zone (Experimental Apartment House)













The difference of floor surface temperature in both zones was around 6K, therefore, the warmer zone could secure warm surface temperature in both cases. Any special difference was not showed in room temperature and floor surface temperature in both cases and it is analyzed that the piping interval adjustment of the warmer and cooler zones were composed equally in both cases.
In the both of single pipeline network and double pipeline network, room temperature and vertical room temperature showed approx. 24~25℃ in the warmer zones and cooler zones both.
Indoor air temperature was vividly mixed due to air convection even if the difference of floor surface temperature occurred and the difference of temperature did not largely occur in one space. So, those were analyzed that similar distribution of air temperature was showed at all vertical/horizontal location.
In the case that the warmer and cooler zones was composed through the piping interval adjustment in single pipeline network, hot-water was supplied during the same period(the warmer zone and cooler zone: about 10 hours), but in the case of double pipeline network, the difference of hot-water supply period largely occurred about 11 hours.
It indicates that the effect on the composition of the warmer and cooler zones by single pipeline or double pipeline respectively showed the difference of hot-water supply period.
In the case that the warmer and cooler zones were composed by single pipeline, hot-water is suppled during the same time even if the heating load required to the warmer and cooler zones is different.
But in the case that the warmer and cooler zones is composed by zoning with double pipeline, the warmer zone that is located at balcony in the room adjacent to outside such as living room requires more heating load than the cooler zone located at the inside of room. So, hot-water is supplied longer time and hot-water is supplied to the cooler zone that requires comparatively less load just in minimum time. It is evaluated to be new concept of Ondol system available for appropriate coping followed by each load requirement if the deviation of load requirement occurred largely in one space.


4. Conclusion

In this study, the Ondol System for warmer and cooler zone, a new concept floor heating system, was developed by improving the performance of floor heating system in the existing apartment houses. And the distribution of the floor temperature of the warmer and cooler zones and the distribution of room temperature were measured and the result was analyzed by comparison for mock-up room and experimental apartment house.
As a result of the research, in the case of single pipeline network, the warmer and cooler zones can be composed using hot water piping interval in one living room. 
In case of double pipeline network, the warmer and cooler zones can be composed using two control point in one living room. 
The Ondol system for warmer zone can be applied  to  reduce cold draft which occurs near the window in the room adjacent to outside or the large living room. The Ondol system for cooler zone can also be applied to reduce hot-water supply in response to heating load in the inside of room.
If the deviation of load requirements in one space largely occur, new Ondol system for the warmer and cooler zone is evaluated available for appropriate coping followed by each load requirement. And it can also be considered to secure much more self-control of thermal environment and flexibility of temperature regulation since the occupants may choose a warmer zone and cooler zone to the desired position.


Bibliography
 1. Cho, D. W. (2007), Research for the development of  district heating system in korea style of apartment houses, 2007. 6
 2. Chun, C. Y., Kim H. J. and Bae N. R. (2005), Research on Thermal Environment in Apartments' Living rooms and Residents' Control Behaviors of a Thermostat , 2005. 8
 3. REHAU(2007), REHAU FLACHENHEIZUNG KUHLUNG


   

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