METHOD AND ARRANGEMENT FOR PREVENTING CONDENSATE FROM DEPARTING IN LIQUID PHASE FROM A COOLING SURFACE

Abstract: Condensate is normally prevented from departing in liquid phase from piping or a cooling surface, said piping conveying liquid at a temperature which may be lower than the dew point of the ambient air, by applying a material layer (3) to the outside of the piping (1) or cooling surface. In such as cooling plants, the surface temperature is allowed to be below the dew point of ambient air, and moisture transport is then carried out in the material layer (3) both in the vapour and liquid phase, and water is caught up in the layer to a certain extent, while excess liquid is taken away by drying out.

Description: METHOD AND ARRANGEMENT FOR PREVENTING CONDENSATE FROM DEPARTING IN LIQUID PHASE FROM A COOLING SURFACE * The present invention relates to a method of preventing conden- 5 sate from departing uncontrolled in liquid phase from a tube, piping or the like or a cooling surface, which is conveying liquid at a temperature that may be below the dew point of the surrounding air, a layer of material being applied to the outside of the tube or cooling surface, thiε layer having an 10 insulation capacity such that the surface temperature can still be below the dew point of the ambient air. It is known to insulate cooling surfaces for preventing conden¬ sation on the tube and liquid dropping from it. Insulated 15 coolant conveying pipes in an indoor climate have a minimum delivery line temperatur of 14°C to such as an air conditioning unit, ceiling mounted cooling elements with or without inlet air, radiation-convection systems for cooling inlet air and heating, in order to deal with the risk of condensation. By 20 lowering thiε temperature a number of degrees, the available temperature drop is increased, and thus the capacity of the installation, or alternatively the plant cost for a given capacity. Insulating the delivery piping with a vapour-proof insulation allows a higher surface temperature to the sur- 25 roundings and the temperature in the piping can be lowered. This method is effective, but expensive, and can not be applied to the cooling elements themselves, since the intended cooling of ambient air would then cease. 30 The object of the present invention is to systematically utilize a moisture - absorbing and capillarily conducting surface layer, , such as to lower the delivery line temperature in a coolant conveying line and cooling elements in a normal indoor climate, without the formation of injurious drops of condensation. Since 35 this object is achieved in accordance with the invention the risk of surface condensation can also be prevented for other types of water piping, e.g. such as are included in roof water removal systems, where the piping is laid under the ceiling inside a building. The features characterizing the invention and fulfilling the purpose mentioned above are disclosed in the accompanying claims. An embodiment of the invention, with variations, will now be described while referring to the accompanying drawing figure. The accompanying drawing figure is a cross section of a tube of an air cooler. A tube 1 thuε contains a coolant at a temperature under the dew point of the air surrounding the tube. The latter iε provided with two cooling fins or flanges 2 for heat exchange with the air. The flanges 2 are specially formed such as to have poorer heat conduction towards their tips, resulting in that the tempe- rature there is above the dew point of the ambient air. On the outside of the tube there is a layer 3 of suitable material that can transport moisture both in vapour and liquid phase. The layer may be εaid to be hygroscopic, and is also applied to a certain extent, or entirely, over the flanges. The layer 3 haε been given a thickness or composition such that the liquid is caught up in it, and since drying out takes place at the tips of the flanges, the layer has the effect of sucking and transporting the liquid out to the tips, where the liquid dries out. This can thus take place if the layer has a suitable thickness and the temperature conditions are correct, which thuε involves that a sufficient amount of liquid may be caught in the layer and dried out to a sufficient extent towards the tips of the flanges. Applicable at the same time is that the thickness of the layer on tube and flanges is minimised such that the coolingeffect is maintained or increased, but even so is sufficient to absorb the condensed moisture and to transport it by capillary action towards the flange tips where, as pre¬ viously mentioned, the temperature is greater and drying-out can take place. With thiε implementation of the cooling tube, the coolant temperature may continously be under the dew point of the ambient air, without risk of condensation from the ambient air and the formation of liquid drops, in spite of maintained or improved cooling effect. Alternatively to the illustrated embodiment, the cooling flanges or cooling surfaces may be connected to the tube in such a way that a weakened thermal contact is obtained, thus causing the details to have a higher temperature, so that drying out can take place there. Another embodiment can also be envisaged with respect to drying out. This can be arranged as periodically occuring drying out occasions before the layer has collected so much liquid that the latter starts dropping from the surface of the layer. Drying out is done by increasing the ambient temperature and taking away the liquid in its vapour phase. Such a method is particularly suitable in air conditioning equipment, where the procedure iε then to raise the cooling water temperature in the coolant line during certain times, and to allow these times to be repeated in a regulated manner, and in relation to the amount of conensate which can conceivably be deposited and accumulated in the layer, so that the period at increased temperature occurs before the condensate departs from the outside of the layer in the form of drops. The regulation can be done with the aid of calculation, or by arranging some form of vigilance device that gives a signal when too much moisture has collected in the layer. When a signal has accordingly been sent, a drying out period can be started automatically. This enables the maintenance of a lower delivery line temperature for the coolant, with consequential smaller piping and pump systems. The coolant temperature or the ambient air temperature has been given a time variable sequence, such that moisture is stored in the layers on the tubes being subsequently dried out . In the latter case there iε intended with the systematic utilisation and adjuεtment of the moisture absorbing layer in respect of its amount and properties, to a known timevariable coolant load in places served by a coolant system. The inventive concept may also be expressed by saying that the tube is insulated with a porous moisture-absorbing composition, such that a given temperature rise towards the surroundings iε obtained, but primarily that the vapour which condenses iε absorbed and stored in the layer until the temperature can be increased, or alternatively the liquid or vapour is led by capillary action to warmer parts of the tube where the moisture can depart .

Claims: CLAIMS 1. Method of preventing condensate from departing uncontrolled in liquid phase from a tube, piping or the like, or a cooling surface, which iε conveying liquid at a temperature that may be lower than the dew point of the ambient air, a layer of material being applied to the outεide of the tube or the cooling surface, the material having an insulation capacity such that the surface temperature can still be below said dew point, c h a r a c t e r i z e d in that moisture is transported in the material layer m both vapour and liquid phase, and in that water is caught up in the layer to a certain extent while excess liquid is taken away by drying out . 2. Method aε claimed in claim 1, c h a r a c t e r i z e d in that drying out is carried out periodically. 3. Method according to claim 1, c h a r a c t e r i z e d in that drying out is carried out at localities on the tube or cooling surface where the temperature is higher due to poorer heat conductivity, the condensate being urged by the effect of the material layer from a moist region to one less moist. 4. Method according to claim 1, c h a r a c t e r i z e d in that drying out is carried out with the aid of details connected to the tube or cooling surface, where the temperature is higher due to given, weakened thermal contact with the coolant, the condensate being urged by the effect of the mate¬ rial layer to said details. 5. Arrangement in the conveyance by piping of liquid at a temperature lower than the dew point of the ambient air, where said piping has been provided externally with an layer (3), the insulation capacity of which is too small to prevent the surface temperature from being above the dew point of the ambient air, c h a r a c t e r i z e d in that said layer (3) iε hygroscopic and with a thickneεε enabling the accumulation of condensate, and in that drying out is arranged for the amount of condensate exceeding the liquid absorption capacity of the hydroscopic layer (3). 6. Arrangement aε claimed in claim 5, c h a r a c t e ¬ r i z e d in that drying out is arranged in the form of a periodically recurring raiεe in temperature of the conveyed liquid, such that the temperature on the outside of the piping (1) is above the dew point of the ambient air solely during such period. 7. Arrangement according to claim 5, c h a r a c t e ¬ r i z e d in that the piping (1) or tube is made with flanges (2) or other surface-increasing means having a worsened heat conductivity, such that surface areas are obtained where the surface temperature is above the dew point of the ambient air, the flanges (2) or surface-increasing means also being covered by the hyroskopic layer (3) for transportating the condensate accumulated in the layer on the outside of the tube (1) to said εurface areas (2). 8. Arrangement according to claim 5, c h a r a c t e ¬ r i z e d in that the tube (1) or cooling surface has connected details having weakened thermal contact with the coolant, such that the temperatures of the details will be raised and drying out can take place there.

Inventors: JOHANNESSON GUDNI, SKOGSTROEM LARS, JOHANNESSON, GUDNI, SKOGSTROEM, LARS
Applicants: NORDINNOVATION AB
Application year: 1992
Main classification: F16L59
IPC codes: F16L59