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Ask many of those same engineers and contractors about radiant cooling systems and you will probably get a mix of confusion, fear of the unknown and dismissal. Cooling with radiant however, offers many of the same benefits as radiant heating; cooling systems that are comfortable, efficient and quiet.
Radiant cooling systems have been widely used in Europe for some time and they are starting to become more popular in North America, especially in the dry climates of Southwest USA. According to Jerry Leyte, Central Canada sales manager for Uponor, there are now quite a few radiant cooling systems installed in Canada. Related: Small scale hydronic cooling. Radiant cooling follows the same principles as radiant heating, but in reverse. Thermal energy is exchanged by radiant heat transfer between the heat loads present in the space and the cool floor or ceiling.
Energy radiates from the objects, people, equipment and lights to the cool surface, which is opposite to what happens in heating mode, where the heated panel radiates to the objects and people. It is possible to have radiant panels that provide both heating and cooling, providing the best comfort and efficiency all year long. There are two broad types of radiant cooling systems, which are chilled slabs and radiant panels.
Chilled slabs offer benefits of integration into the building, lower installed cost and increased thermal mass. Radiant slabs can be arranged so that they are exposed on both sides, providing, at different times of the year, radiant heat to the space above and radiant cooling to the space below.
Radiant cooling slabs use similar design and sizing principles as a hydronic radiant floor system, using the same types of PEX pipes, manifolds and pumps as in heating. Chilled water between 55F to 58F is circulated through the pipes, which are embedded in either floor or ceiling. Radiant cooling slabs require a close tube spacing of six to nine inches on centre, which is a little tighter than the nine to in.
Radiant cooling can also be delivered through specialized panels, which would typically be attached to ceilings, but can also be attached to walls. Panels offer installation flexibility in terms of where they can be placed and how they are integrated with dropped ceilings, lights and other electrical systems. The lower thermal mass of panels allows them to react very rapidly to changing loads.
Radiant cooling panels are designed so that they can be retrofitted into the ceilings of older buildings as the plenum space requirement is minimal relative to fan coil units or VAV systems.
Typical radiant cooling installation methods. Image courtesy Uponor. Cold water circulation through PEX pipes. Radiant cooling surfaces mounted in perimeter zones. Chilled water is circulated through the concealed pipes. Plastic pipes can be covered with all usual building materials. Perceived temperature: a numerical average of mean radiant temperature of surrounding surfaces and the room air temp.
Radiant Cooling System Components. Small air handling unit to control humidity. Radiant Cooling System Configurations: Radiant cooling can be integrated within any type of surface depending on feasibility for a specific application Ceiling based radiant cooling is the most energy-efficient configuration; the direction of convection currents developed are congruent with the temperature gradient i. Radiant Cooling System Configurations. Radiant Floor Cooling and Heating. Radiant Wall Heating and Cooling.
The Operation Schematic includes:. Operation Schematic Diagram of Radiant Cooling. The pipes can be embedded in the slab. The pipes can be installed in plastering on the ceiling instead of being embed in the slab.
The pipes can be laid to form different zones. Performance of COP at higher chiller operating temperature. Low air volume and hence duct sizes are significantly reduced. Commercial Area — office spaces, schools, and few applications in hotels. Residential — in homes, in areas where humidity is less. Industry- Capillary tubes may be used for an industrial application, as well as a fire suppression system Hospitals and Laboratories — Radiant cooling can be effective to maintain a clean environment in hospitals and laboratories.
However, individual decentralized boilers are used relatively often for residential buildings in Korea. Therefore, the whole system needs to be simplified in terms of the initial cost, system control, and maintenance.
This is even more necessary for small residential buildings. In this study, a strategy for the configuration and arrangement of an RFCS using an individual cooling source was derived for application to residential buildings in hot and humid summer climate regions, such as Korea.
Then, the feasibility of this system for a residential building was verified through the field test, by evaluating the performance of space cooling and surface condensation prevention.
In order to accomplish this, the cooling load, system requirement, and configuration of the existing heating and cooling system were investigated. From these results, a strategy for the configuration of the whole RCS for application to residential buildings using individual heat production units was derived.
In order to derive an alternative configuration of the whole RCS for residential buildings using individual heat production units, previous research Jeong et al. RCS can remove only the sensible load. Therefore, a dehumidification system is additionally required to remove the latent load for the prevention of surface condensation. The comfort requirements of the floor surface temperature also have to be satisfied, because when the existing radiant floor heating panel is used for cooling, the floor surface used as the radiant cooling panel is in direct contact with the human body.
The cooling capacity of a Radiant Floor Panel RFP calculated based on this method may be insufficient for space cooling when considering the simulation result for cooling load in the above research Jeong et al.
Thus, it can be inferred that supplementary cooling equipment is required in addition to the RFP. From the above investigation, applying the RCSs to residential houses in hot and humid summer climate regions requires dehumidification equipment, to remove the latent load and to prevent surface condensation; and supplementary cooling equipment, to remove the sensible load beyond the cooling capacity of the radiant panel.
However, the respective installations of all of these systems in a house increases the burden in terms of the initial cost, area occupied by the equipment, control of the whole system, and maintenance. Thus, the system configuration needs to be simplified. The application of cooling-based dehumidification, which can perform both dehumidification and cooling, can be considered.
Supplementary cooling equipment with dehumidification can also be considered, which uses the same heat transfer medium, in order to avoid an increase in the number and kinds of heat sources. Therefore, the Fan Coil Unit FCU was selected as the additional system for dehumidification and supplementary cooling, because the FCU is typical equipment that uses water as the heat transfer medium, as does the radiant panel, and adopts the cooling-based dehumidification.
In order to establish a strategy for the configuration and arrangement of the whole RCS, the configuration of the heating and cooling system for a residential house in Korea was analyzed through corresponding statistical data Korean Statistical Information Service. It was also found that indoor package air-conditioner units tend to be installed only in the living room, or in the living room and only one bedroom 1.
Based on the analysis results of the requirement for applying RCSs in residential buildings with individual heat sources, and the configuration of existing heating and cooling systems for residential buildings with massive concrete slab, it has been determined that the whole cooling system should consist of RFCS and supplementary cooling equipment combined with dehumidification, and should be installed in a similar manner to the existing radiant heating system and PAC systems.
Because the existing radiant floor heating panel can be used as the radiant cooling panel, it has been determined that a radiant floor cooling panel for space cooling should be adopted for every thermal zone each room. For the supplementary cooling equipment with dehumidification, installation in every room may lead to sufficient dehumidification and supplementary cooling, but this may be unreasonable in terms of cost, system control, maintenance, and required area, because of the multi-zone space.
In addition, while bedrooms are mainly used during bedtime and have a relatively low latent load, a living room may have substantial latent load, because of the direct influence of cooking, laundry, and drying, as well as its proximity to the bathroom.
Thus, it has been determined that supplementary cooling equipment with dehumidification should be installed in a representative room, such as a living room, rather than being installed in every room.
The performance evaluation of a heating and cooling system is generally conducted under a specific condition that represents the operation environment for the system.
However, various conditions that arise during the real operation of a system may not be reflected in these evaluations. In particular, this is more apparent for residential houses with irregular load profiles.
Therefore, in this study, in order to assess the feasibility of RFCSs for residential houses under real operation environments, the field test was conducted over one month in August, when it is hottest in Korea.
A dormitory house with four thermal zones located at Seoul National University in Korea was selected for the field test. This house has a living room, a bathroom, three bedrooms, and a balcony on the north side of the living room Fig. Two bedrooms are equipped with a bed and one bedroom is equipped with a mattress, so as to reflect the traditional Korean sleeping style. A total of 16 persons participated in the field test during the whole test period, with four persons each day, which is similar to the number of occupants of a typical residential house in Korea.
The existing RFP based on the heating load was used for cooling, but the design water flow rate for cooling was calculated and supplied. The FCU, as the supplementary equipment for dehumidification and additional cooling, was installed on the window side of the ceiling of the living room. Based on sensor-measured values in each room, if the difference between the radiant floor surface temperature and the indoor dew point temperature was less than 1 K, the FCU was turned on for dehumidification.
In contrast, if the difference between room temperature and set room temperature was more than 0. Table 2 shows detailed information related to the field test, and Fig. The field test was performed under conditions without any artificial restrictions on the activities of participants.
Participants slept, ate, washed, and dried their clothes freely, just like real occupants would in a residential house. In other words, they were living freely, without any constraints. This ensured that the real feasibility of the system was evaluated under various situations that can occur in a real residential house. The occupants set the target room temperature that they wanted to be maintained for thermal comfort through the system operation.
Thus, the cooling performance of the system was evaluated in terms of maintaining the target room temperature set by occupants.
Therefore, in this study, the performance of cooling and condensation prevention of RFCSs for residential buildings with massive concrete slab was evaluated through a field test in which the occupants freely set the indoor set-point temperature and acceptable minimum floor surface temperature for thermal comfort.
The cooling performance of the RFCS was analyzed in terms of whether the indoor set-point temperature set by the participants was met. The condensation prevention performance was analyzed based on whether the floor surface temperature was kept higher than the room dew point temperature.
In particular, because the supplementary equipment for dehumidification and additional cooling FCU was installed only in a representative room the living room , the condensation prevention performance was analyzed for the living room, as well as for each room. The participants could modulate the set-point temperature to 0.
The indoor set-point temperature, room temperature, indoor relative humidity dew point temperature , and floor surface temperature were measured and recorded in order to evaluate the performance, and a post occupancy evaluation was conducted. Part of the recorded data of the indoor air temperature set by the occupants of Room 1, where occupants set the most varied cases of the set value during the field measurement, is shown together with the corresponding outdoor air temperature in Fig.
As shown in Fig. According to the frequency analysis during the whole test period Fig. These can be considered to be the result of thermal radiation transfer by the RFCS. For this reason, the same thermal comfort level is expected even if the indoor temperature is set approximately 1 K higher, as compared to a conventional air system. Occupants could set the acceptable minimum floor surface temperature so as to avoid discomfort by the floor surface temperature.
According to the frequency analysis of the setting value for the occupied period Fig. Because the human body comes in direct contact with the RFP due to the sedentary Korean lifestyle, it can be inferred that the set value for the minimum floor surface temperature is higher than international standards.
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