TWA Panels
Twa Panels is located in Alberta, Canada dealing in the manufacturing and distribution of the Frenger line of Radiant Heating and Cooling Panels. Twa's radiant panels are an energy and cost saving method of heating and cooling, that provides comfort to a room, much the same way as the sun warms the earth. Radiant heating and cooling panels offer a number of advantages over conventional heating and cooling systems and can be easily modified to fit your needs and specifications.
RADIANT HEATING
Description
Radiant panel ceiling systems are similar to other air-water HVAC systems with respect to the arrangement of its components. The important difference is that room thermal comfort is maintained primarily by radiant heat transfer instead of convective heat transfer (as is the case with tube and fin baseboard radiation).
Advantages
The principal advantages of radiant panel heating systems:
- Comfort levels can be better than those of other conditioning systems because radiant loads are treated directly and air motion in space is at normal ventilation levels.
- Space conditioning equipment is not needed at the outside walls, simplifying the wall, floor and structural systems.
- Almost all mechanical equipment may be centrally located, simplifying maintenance and operation.
- No space is required within the air conditioned room for mechanical equipment. This is especially valuable in hospital patient rooms and other applications where space is at a premium, where maximum cleanliness is essential, or where it is dictated by legal requirements.
- Draperies and curtains can be installed at the outside wall without interfering with the space conditioning system.
- Cooling and heating can be simultaneous, without central zoning or seasonal changeover when four pipe systems are used.
- Supply air quantities usually do not exceed those required for ventilation and dehumidification.
- The modular panel concept provides flexibility to meet changes in partitioning.
- A 100% outside air system may be installed with less severe penalties in terms of refrigeration load because of reduced air quantities.
- A common central air system can serve both the interior and the perimeter zones.
- Wet surface cooling coils are eliminated from the occupied space, reducing potential for septic contamination.
- The panel system can use the automatic sprinkler system piping (see NFPA standard 13, Chapter 3, Section 3.6). The maximum water temperature must not fuse the heads.
- Radiant panel heating and cooling and minimum air quantities provide a draft-free environment.
- Peak loads are reduced as a result of thermal energy storage in the panel structure, exposed walls, and partitions.
- Panels can be coupled with other conditioning systems for heat loss (gain), compensation for cold or hot floors, windows, etc.
Cost and Energy Savings
Energy Savings
A radiant heating system is a much more efficient means of heating an environment than a forced flow system. The cost savings from heating hydronically, as opposed to heating with air, can be as much as 25% in fuel cost alone. This is due to the fact that water is a much better medium to transport heat than air is. The actual amount of energy saved is dependent on many factors including how well the building is insulated, the building size, and the climate the building is located in.
Maintenance Costs
Because radiant panels are out of the way, they are not likely to sustain damage from everyday activities. This is particularly important in high traffic areas such as airport walkways where large numbers of people are walking by with baggage or luggage. Also, since the panels have no dust collecting surfaces, they do not need to be taken apart to be cleaned. This means that the panels will not require periodic repainting due to scratches, dents, or cracking that would be caused by disassembly. Cost savings would be realized during building retrofits, or renovations, by using modular radiant panels that can be reused in other locations without any difficulty.
Construction Costs
There are many ways in which radiant panels can save money in the construction of new buildings. One such area is the amount of pipe it takes to connect to radiant panels. Because both the radiant heating panels and the hot water mains are located in the ceiling, there is no need to drop pipe connections down the walls. All the pipework is up and out of the way.
Increased Floor Space
For office or apartment buildings, the leasable area of a room would be reduced by any wall mounted mechanical equipment around its perimeter. Due to the fact that the panels are up in the ceiling, this space is kept free. This means that the total floor space is no longer reduced by the space conditioning equipment.
Frequently Asked Questions (FAQ)
How Is It Different From Conventional "Radiation"?
Heat may be transferred by conduction (warmth transferred by objects that are touching each other), or convection (heat that is carried from a warmer to a cooler body by an intermediate fluid such as air) or by radiation. Most conventional tube and fin "radiators" are in fact, convectors. They heat a space by warming the air that passes by the heated fins. This air, now warmer than the surrounding air, rises due to buoyancy. This is known as free convection. Where the air is moved past the fins by a blower or fan it is called forced convection. In either case the idea is the same, to compensate for perimeter heat losses by circulating warm air within the space.
By contrast, between 75 and 90 per cent of the energy from a radiant panel is propagated by thermal radiation. Thermal radiation is an electromagnetic radiation propagated due to a difference in temperature. Therefore, the heat is transferred to all bodies "seen" by the panel that are at a lower absolute temperature than the panel itself.
Why Are The Panels In the Ceiling?
It is often asked "Why put the panels in the ceiling? Heat rises, doesn't it?" The answer is no, heat does not rise. Warm air rises. The panels are most effective in the ceiling because from there, they are best able to "see" the objects in the room. Lights are placed in the ceiling for maximum effect. This is because from above, it is not obstructed by room objects and its light can be most effectively cast on the surroundings. Light is a type of electromagnetic radiation which has a shorter wave length than thermal radiation. Therefore, as with a light, the optimal location for a radiant panel is the ceiling.
Another reason for placing the panels in the ceiling is so that higher surface temperatures can be used. The rate of radiant heat transfer from the panel is governed by the Stefan-Boltzmann Law, q = S Ts4 , which demonstrates that the radiative heat transfer from a body increases dramatically as its temperature is increased. Radiant ceiling panels are typically operated at 79-85°C (175-185°F). On the other hand, were the radiant panels mounted on the walls or near the floor, safety code dictates that the panels could not be operated at high temperatures. Thus by placing the panels in the ceiling, the panels can be made to produce more output per area by simply increasing the water temperature.
Is this a Proven Technology?
Radiant panel technology is not new to the HVAC (Heating, Ventilating and Air Conditioning) industry. It is a mature, proven technology that has been in use in Europe for over 100 years. Over the last 35 years, the Canadian and United States HVAC industry has employed radiant panels in many commercial and institutional settings. In fact, since the much publicized outbreak of Legionnaire's disease (spread by contaminated central air systems), radiant heating systems have been the choice for U.S. Veteran's Administration Hospitals and, in the last 10 years, over 80% of the new hospitals constructed in the provinces of Western Canada have employed radiant panel ceiling heating systems.
What About Cold Feet..Warm Head?
Cold feet? Hardly. Tests have shown that the floors in a room heated by a radiant panel ceiling exhibit temperatures 1 to 2°C (3 to 4°F) above the ambient air temperature and actually provide a source of re-radiated heat themselves. In fact, where down drafts from cold walls or glazing present design challenges with respect to occupant comfort, radiant panels provide a solution. The ceiling panels warm the wall or window surfaces by direct transfer of radiant energy, significantly increasing the temperature of each. It has been found that even under extreme cold wall conditions (27°F, -2.7°C), the air velocities are non-draft in nature (less than 50 fpm or 0.25 m/s).
Typically, radiant panel surface temperatures are 170 to 185°F (about 82°C). This can cause the directional mean radiant temperature (DMRT) to be 16 to 20°C (30 to 40°F) above the ambient air temperature. By contrast, on a sunny day, the DMRT outside is 30 to 40°C (50 to 70°F) higher than the ambient air temperature. So, if you enjoy being out in the sunshine, you will enjoy the indoor warmth of a radiant panel ceiling.
RADIANT COOLING
Description
Radiant cooling panels, although relatively rare in North America, have been used successfully in European applications for at least 15 years. Radiant cooling follows the same principles as radiant heating, but in reverse. Thermal energy is exchanged between the heat loads present in the space, and the cool ceiling.
Radiant Cooling Panels
To ensure air quality and removal of the moisture load in the room, radiant cooling panels need to be used in conjunction with a small ventilation system. However, since radiant cooling systems do not use forced air flow to facilitate cooling, a uniform cooling gradient in the room is created. With this reduction in draft, radiant cooling panels provide a very comfortable environment for the occupants of the cooled space.
Advantages
The principal advantages of radiant panel
heating systems:
- Operational costs are reduced for the mechanical chilling system since cooled ceilings operate at relatively high temperatures (average surface temperature of 16°C or 61°F).
- Chillers can operate at higher temperatures resulting in an increase in efficiency and reduction in energy costs.
- Radiant panels can be used as both heating and cooling panels reducing the amount of equipment and piping required compared to conventional heating and cooling system.
- Cooled ceilings are silent and virtually draft free since air flow volumes are reduced compared to conventional systems (typical radiantly cooled office building: 2 to 3 air exchanges per hour compared to 6 to 10 with conventional systems).
- Radiant cooling panels can be retrofitted into the false ceilings of older buildings as the plenum space requirement is minimal relative to fan coil units or VAV systems.
- Smaller plenums result in savings in building height (1' per floor!) compared to air conditioning systems.
Cost and Energy Savings
Energy Savings
A radiant cooling system is a more efficient means of cooling an environment than a forced flow system. This is due to the fact that it is much easier a task to pump water, than it is to blow air. The actual amount of energy saved is dependent on many factors, including how well the building is insulated, the building size, and whether or not the system takes advantage of free cooling.
There have been a few studies on the energy savings created by radiant panels. International Energy Studies have performed tests of Hydronic Radiant Cooling in a High-rise Office Building in Oakland, California, which demonstrates some of the cost savings associated with this technology.
The Lawrence Berkeley National Laboratory also have performed studies of the energy savings of Hydronic Radiant Cooling Systems.
Maintenance Costs
There is very little involved with the maintenance of a chilled ceiling. Once correctly installed, the radiant panels themselves would require little or no further maintenance. This is due to the fact that they have no moving parts, and that they are up and out of the way. The other equipment such as water pumps, control valves, dew point sensors, and chillers, would require some maintenance, but these would be standard operations. Less maintenance would be required for the air handling and air conditioning units due to the reduction in size and load required by the building.
Construction Costs
Although the costs associated with the supply and installation of a radiant ceiling may be slightly higher than a forced air system, there are other significant savings that should be taken into consideration. The first and foremost saving is that of space. Because the required air volume has been reduced, the need for large amounts of duct work above the ceiling has been greatly reduced.
This means that the plenum height could be reduced by approximately one foot per floor! A reduction in plenum height can be translated into a reduction in overall building height. If this technique were to be applied in the construction of a ten-story office tower, the total height of the building could be reduced by ten feet'. This would translate into significant savings in material and labor in the construction of the building's structure.
Applications
Radiant Cooling
Panels
Radiant cooling panels are mainly used in public buildings. These include: hospitals, office buildings, libraries, museums, schools, nursing homes and many more. Radiant cooling panels can be installed anywhere radiant heating panels are used.
Frequently Asked Questions (FAQ)
How Does Radiant Cooling Work?
Radiant cooling follows the same principles as radiant heating. The heat transfer occurs between the space and the panels through a temperature differential. However, unlike radiant heating, the colder ceiling absorbs the thermal energy radiating from people and their surroundings. The major difference between cooled ceilings and air cooling is the heat transport mechanism. Air cooling uses convection only, whereas cooled ceilings use a combination of radiation and convection. This amount of radiative heat transfer can be as high as fifty five per cent, while convection accounts for the remainder. With cold ceilings, the radiative heat transfer occurs through a net emission of electromagnetic waves from the warm occupants and their surroundings to the cool ceiling. On the other hand, convection first cools the room air due to contact with the cold ceiling, creating convection currents within the space which transfers the heat from its source to the ceiling where it is absorbed.
What About Condensation?
Condensation on the surface of the panels is not a problem with radiant cooling. Since condensation of water occurs when the dew point temperature is reached, proper water temperature control will help avoid any condensation. To prevent the formation of condensation, a sensor monitoring the dew point temperature of the room is used in conjunction with a controller which modulates the inlet water temperature accordingly. Therefore, if a risk of condensation is present, the water temperature is raised or the water flow is shut off. However, since the lower the panel's inlet temperature is, the more work the panels do, the inlet temperature should be determined to be as close as possible to the room's dew point temperature. Consequently, the cooling capacity of a radiant cooling system is generally limited by the minimum allowable temperature of the inlet water relative to the dew point temperature of the room air.
Is Radiant Cooling Appropriate for Residential Applications?
Unfortunately radiant cooling is not a good choice for residential houses.
Radiant panels require the air in the space to be dehumidified and controlled
very carefully. In a residential home, the ability to open windows or leave
doors ajar, would allow humid outside air to enter the space. This could raise
the dew point temperature to a point where to avoid condensation, the radiant
panels would have to operate at relatively high temperatures. Since the panel's
cooling capacity is dependent on the temperature differential between the panels
and the room temperature, having to raise the panel temperature to avoid
condensation would severely hamper the panel's cooling ability.
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