METHOD AND DEVICE FOR THE SUPPLY OF COOLING AIR

Abstract: Method and device for supply of cooling air to a room from the room ceiling (1), where cooled air is led through an air channel (3) in the ceiling, to at least one air supply device (4) in a ceiling element (2) formed of a heat conductive material, where the cooled air is allowed to sink down in a part of the element (2) which is shaped as a basin, the cooled air is allowed to cool the element (2), which then cools the room air by radiation and convexion, and to allow the warmed air to rise to the upper part of the element (2) where the air is led out in the room through slits (5) to be distributed in the room.

Description: METHOD AND DEVICE FOR THE SUPPLY OF COOLING AIR The present invention relates to a method and a device for draft-free supply of cooling air to personnel rooms. In modern professional buildings, the demand for cooling of personnel rooms is greater than demand for heating. This is especially true for office buildings where light, office machines and people, plus sunshine through the windows, may create a significant surplus of heat. Cooling of personnel rooms is in terms of ventilation engineering far more demanding than heating. While a stream of warm air feels comfortable in a room that needs heating, will a noticeable stream of cooled air in the warm room feel uncomfor- table, and will often be perceived as a draft. When a large demand for cooling is to be met with cooled ventilation air, which is common in modern ventilation systems, could this be done with a small amount of strongly cooled air, or with a less supply of moderately cooled air. In practice, the supplied air should not be colder than 8-10 °C below the room temperature in order to avoid so-called cold*, (vertical streams of cold air along walls and windows), uneven room temperature or a feeling of draft. Less cooling of ventilation air means a correspondingly larger amount of supplied air, which means a relatively expensive supply- and distribution system for the cooled ventilation air in order to avoid noticeable air streams in the room. Noticeable air streams gives a feeling of draft, even with small temperature differences. Large amounts of air also means higher air speeds in the ventilation system. This presents* increased demands to sound insulation of the system in order to avoid bothersome noise from the ventilation system. The problem with a large demand for cooling may be solved by building in cooled surfaces in the room rather than basing the whole cooling on ventilation. Such a cooled surface must lie in the ceiling in order to avoid cold* from the walls or a room with cold floor. Cooling ceilings is known from the ventilation engineering. The ceiling in the room will be partly or totally cooled down with built-in piping loops with cold water or a cooling medium. Built-in channels with cooled air is also used. Such cooling feeling give a comfortable and uniform cooling effect, partly by radiation and partly by draft-free natural connection. Cooling ceilings may be used alone or in combination with traditional cooling through the ventilation system. Cooling ceiling reduces the demand for air cooling, so that the cooling air may be supplied without draft problems. Cooling ceilings are, however, an expensive solution, and therefore it is no longer widely used. According to the present invention, one can achieve cooling of personnel room that gives the same advantages as a cooling ceiling in combination with traditional air cooling with ventilation, but without high costs incurred by the use of cooling ceiling. These advantages are achieved with the method and device according to the invention as defined by the features set forth in the claims. Figure 1 of the drawing shows schematically a side view of the device according to the invention, mounted on a ceiling in a room, and figure 2 shows a corresponding view another embodiment. Below the ceiling 1 in the room to be ventilated and cooled, is built in an open lining or a ceiling element 2 consisting of a plate of a heat conductive material. In the preferred embodiment of the invention, this is a single metal plate with a rounded shape, which forms a limited basin for ventilation air under the ceiling of the room. A moderate amount of ventilation air, cold enough to meet the entire rooms demand for cooling, is supplied to the air basin above the ceiling element 2 with a ventilation channel 3 and one or more supply devices for, which distribute the air uniformly and very low speed into the air basin over the ceiling element 2. The cold air sinks naturally down to the bottom of the basin and cools the ceiling element 2, which thereby functions as a cooling ceiling for the room below. As a result of the cooling effect will the ceiling element absorb heat from the room, partly through radiation, partly through convection, and this heat will be transferred to the cooling air and increase its temperature. The cooling air which is prewarmed in this way rises naturally up and passes further into the room as ventilation air through slits 5. This air is still cool, but no longer so cool that it gives any effect of draft in the room. The large area of the slits 5 causes the air speed to be low, in the area of 0,2 to 0,6 m/sec, and causes therefore no air motion or streams that can be perceived as draft in the room (diffuse air supply). The ceiling element 2 according to the invention may have various shapes, for example with convex outside shape shown on figure 1, or a plane shape as shown on figure 2. The shape in terms of air flow, must, however, be such that the most prewarmed cooling air passes out in the room through the slits 5. The convex shape shown in figure 1 is considered the most suitable, but other shapes, for example concave, is entirely possible for example as a result of architectural or other demands. The ceiling element 2 may be made in metal or other material. A sound dampening layer on the lower side of the element or a double plate where the lower plate is perforated, may often be desirable because of the acoustic conditions in the room. According to the invention, however, must the entire element have sufficient heat conductivity to transfer the necessary part of the cooling effect of the air through the material of the element 2, and from there to the room. A lower conductivity, as for example a thin building plate, will demand a correspondingly larger area of the element 2 to create the same effect. It is also possible to increase the heat conductivity by using a corrugated plate or a plate with ribs or similar. By the preferred embodiment of the invention, the cooling air from the ceiling element 2 may be 30-50 % of the rooms need for cooling, while the prewarmed cooling air from the slits 5 covers the remaining demands for cooling. The temperature of the ventilation air from the channel 3 may be 12-14 °C lower than the room temperature without creating the effect of draft in the room. Typical cooling capacity for ceiling element 2 is in the area of 30-60 W/m 2 . A supply device for cooling air to room cooling according to the invention presents demands to the purity of the supplied cooling air. It must contain a minimum of particles that could be deposited as air in the bottom of the air basin over the ceiling element 2. Such a layer of dust will reduce the heat conductivity through the element, and dust could be blown out in the room when the amount of cooling air increases . It has been found suitable to make the supply devices 4 as one or more filter bags in order to separate dust from the cooling air, which are replaceably mounted on the air channel 3. With the preferred embodiment of the invention, the ceiling element 2 is sectioned and turnably mounted on the ceiling, so that it can be turned down for cleaning on the top side and for replacing of the filter bags as a part of routine maintenance. These embodiments are however practical matters, and no prerequisite for the device to function according to the purpose.

Claims: Patent Claims 1. Method for supply of cooling air to a room from the ceiling (1), CHARACTERIZED IN that the cooled air is conducted through a air channel (3) in the ceiling, to at least one air supply device (4) in a ceiling element (2) made of a heat conductive material, letting the cooled air sink down in a part of the element (2) shaped as a basin, allowing the cool air to cool the element ( 2 ) which then cools the room air by radiation and convection, and to allow the such warmed air to rise to the upper part of the elements ( 2 ) where the air is let out in the room through slits (5) to be distributed in the room. 2. Method according to claim 2, CHARACTERIZED IN by the leading the air through the slits ( 5 ) with a air speed in the area of 0,2-0,6 m/sec. 3. Method according to claims 2 and 3, CHARACTERIZED IN that the cooling air is supplied from the channel to the element (2) in a diffuse manner, preferably through replaceable filter, for example in the form of filter bags. 4. Device for supply of cooling air to a room from the room ceiling (1), CHARACTERIZED IN that a pan-shaped ceiling element ( 2 ) of a heat conductive material is mounted in the ceiling ( 1 ) and surrounded by at least one air supply device ( 4 ) in the ceiling element (2), that the air supply device (4) is connected to a air channel (3) for supply of cooled air, and that slits (5) are provided in the ceiling element (2) near the ceiling to allow a somewhat warmed cooling air to flow into the room. 5. Device according to claim 4, CHARACTERIZED IN that the ceiling element (2) depending from the ceiling is sectioned and may be lowered for cleaning and maintenance. 6. Device according to claims 4 and 5, CHARACTERIZED IN that the ceiling element (2) is covered with or has mounted on it an acoustic dampening layer on its lower side. 7. Device according to claims 4-6, CHARACTERIZED IN that the ceiling element (2) is shaped with a concave bottom. 8. Device according to claims 4-7, CHARACTERIZED IN that the ceiling element (2) is shaped with a convex bottom.

Inventors: BAKSTAD PER, ROESSEL STEIN, SKOGEN OLE JAN, BAKSTAD, PER, ROESSEL, STEIN, SKOGEN, OLE, JAN
Applicants: ABB MILJOE AS
Application year: 1998
Main classification: F24F5
IPC codes: F24F1, F24F5