Method and device for drying laundry using district heating

Abstract

 Method for making use of district heating by through this feeding generated heat is fed to drying cabinets or tumble dryers via a heat exchanger (1). The heat exchanger is arranged separately from the drying cabinet or dryer. The heat exchanger can advantageously be connected directly to the high-temperature water pipes of said district heating and arranged close to the heat exchangers for radiator water, hot tap water or a high-temperature water loop feeding the air heaters in ventilation facilities or the like. The air heated in the heat exchanger is then through one or more tubes (2) fed to one or several drying cabinets and / or tumble dryers. The air is fed to the inlet of respective drying device and the air is then passed out from the drying devices in a conventional manner, i.e. for example, into the surrounding environment (outdoor or just out into the room).

Description

[0001] The present invention relates to the efficiency and environmental benefits of district heating. Admittedly district heating initially include relatively high costs for district heating central as well as associated distribution net of high-temperature water and heat exchangers, etc. at the heat consumers but it is more efficient and cleaner for the environment than many small in different ways powered heating units and therefore it is also economically more efficient.

[0002] In light of the above problems the object of the invention is to improve the use and increase the environmental benefits of district heating.

[0003] The above object is, in accordance with the invention, solved by the use of district heating for drying laundry. Since district heating is cheaper than electricity not only money is saved, but as a result of the district heat generation in the district heating plant having a high efficiency an over all save of energy is obtained, achieving an environmental benefit.

[0004] Primarily drying cabinets fitted with a district heat connected air heater is a practical embodiment, but one can also consider the use of tumble dryers heated by district heating.

[0005] The connection of the drying cabinet to district heating is advantageously via the high-temperature water system used for example for heating the air in ventilation systems. Due to the high temperature of the water the air heater volume as well as cost can be kept lower than what otherwise would have been the case.

[0006] Heat regulation can be executed by a thermostatic valve in the connection to the heat exchanger. One can also imagine a by-shunting of the drying air so that only a portion is heated by the heat exchanger and a portion is by-shunted so that the desired temperature is obtained.

[0007] If supply of high-temperature water is missing one could imagine using the system for domestic heated tap water that is normally running even in summer and as a result of its relatively high temperature can heat the drying air, allthough not as high and hot as high-temperature water. The circulation of heated water to the heat exchanger can be provided by the circulating pump for the heated domestic tap water. This pump is actually only there to ensure that heated water constantly is available everywhere in the house, without the water having to run for a while, and may therefore have to be increased in size if heated tap water is to be used to heat drying cabinets.

[0008] The connection to the loop for heated tap water can comprise a thermostat that is placed so that the heated air flow pass its sensor.

[0009] The use of district heating in drying cabinets makes these more expensive, not least in terms of installation and is from this point view no obvious measure, but since otherwise unused energy may be used for more than half of the year it is actually profitable. For the operator of the waste burning this excess energy is free and can thus be sold at a sufficiently low cost to be interesting for users of drying cabinets.

[0010] By using otherwise unused energy for drying instead of electric energy an environmental gain is obtained.

[0011] The use of district heating also provides a more secure installation since electricity and dust is no good combination for security reasons.

[0012] Additional advantages and features of the invention are apparent from the following description of an advantageous embodiment in connection with the attached drawing. In the drawing figure 1 shows a heater for drying air according to the invention seen from a first side and figure 2 the same heater for drying air in a view perpendicular to that in figure 1.

[0013] The drying air heater shown in the drawing includes an inlet 1 for air from a drying cabinet or a tumble dryer. This air that has absorbed moisture is passed through a filter 2 and then to a heat exchanger 3 (air-air) that cools the humid air so that some of the moisture in the air is condensed. The condensate is collected in a tray 4 below the heat exchanger and led from this with a condensate drain 11 further to an adequate outlet. From the heat exchanger the now dryer air is led to an air heater 5 (water-air heat exchanger) which is heated by water, either in a local heating net of the property or by in a district heating net circulating water. From the air heater air is fed through an air outlet 12 further back to the air inlet of the drying cabinet or tumble dryer via a blower 6 which sucks air from the drying cabinet or tumble dryer through the above described heater for drying air and then push the air back to drying cabinet or tumble dryer.

[0014] The heat exchanger is cooled by air supplied through an inlet 7 and that is discharged through an outlet 8. The cooling air may for example be taken from the building exterior and also returned there. The transport of cooling air is made by a fan, for example, duct fan 13 which sucks the air out of the outlet 8.

[0015] Connected to the heat exchanger 3 is a damper 9 which, if necessary, can be opened to lead a major or minor part of the air past the heat exchanger, for instance at the formation of ice in the heat exchanger.

[0016] From the air duct for exhaust air from tumble dryer or drying cabinet to the heater for drying air there is a branched off duct to the outside air which duct is equipped with a damper. Also in the duct from the heater for drying air to drying cabinet or tumble dryer there is a corresponding damper fitted branching to the outside air. In this way drying can when the outdoor air is dry take place by simply exchange air in drying cabinet or tumble dryer, but without heat. As an alternative, you can divert air to the surrounding from the space in front of the heat exchanger. Possibly, one could imagine to mix the outgoing air with outlet air from the cooled side of the heat exchanger. This cools the hot used drying air down a first step by the colder exhaust air from the cold side of the heat exchanger. Since this is cold air that is heated it is dry and can therefore absorb moisture and reduce or eliminate the tendency to condensation that would otherwise normally result when hot drying air is released outdoors. Furthermore, you can use a common fan for the diversion of some of the used drying air to the surroundings and for the cooling air from the cold side of the heat exchanger.

[0017] In the above-described manner air fed to the building's exterior can be replaced by cold outside air that flows into, for example an inlet to an air distribution space in front of the air heater.

[0018] A reduction of emission of moist condensing air eliminates or reduces frost damages and wear of the facade.

[0019] If the building's ventilation system and heat recovery system are sufficiently dimensioned, or the total drying need is moderate, it is conceivable that the ducts that go to the outside of the property has connectable ducts ending in the laundry room.

[0020] The heating unit can be arranged at the side of or on top of the drying cabinet or tumble dryer.

[0021] The air heater can advantageously be connected directly to the high-temperature water pipes of the district heating network and arranged in connection with the heat exchangers for radiator water, domestic hot tap water or a high-temperature water loop feeding the air heater in the ventilation facilities. The heated air can be fed through tubes 2 to one or several drying cabinets and/or tumble dryers. The air is fed to the respective drying device to its inlet and the air is then passed out of the drying device in a conventional manner, i.e. for example the environment (outdoor or just out in the room).

[0022] The air temperature supplied from the drying air heater may be temperature regulated by controlling the high-temperature water inflow with a bypass and a three-way valve between inlet and outlet pipes for the high-temperature water, or with a circulation pump. Pump or bypass can be controlled with a temperature sensor in the outlet channel for the hot air. Alternatively, a thermostatic device can be used. In order to individually control different drying cabinets or tumble dryers, you can provide them with air bypasses or dampers that can also be used for setting different desired drying temperatures.

[0023] The outlet air from tumble dryer or drying cabinet can be returned to the inlet side of the heater for drying air. Since the air heater in this way reach a higher initial temperature for the air also the outlet temperature to drying cabinet and/or tumble dryers will be higher enabling in turn a faster drying. The temperature in the air duct back to the air heater also increases so that the temperature difference relative the room air is increased. With a return air tube of metal a chilling of the return air is obtained, which provides a condensation of some of the moisture in the return air that become more dry and thus dries better. The condensed water can be discharged at an appropriate location. To enhance the above effect one can even arrange a condenser in the return tube for air back into the heat exchanger. Room air can be blown through the condenser with a fan. A filter can advantageously be positioned in front of the condenser in the return air tube.

[0024] One does not necessarily need to circulate back all the air, but one can imagine that some of the return air is discharged into the room (after passage of the condenser or return tube) and replaced with fresh room air. The proportions between the added and recycled air can be controlled with a damper. Possibly, one could imagine thermostatically controlled dampers at each drying device for individual control of their drying temperatures, although a common device is used for the supply of drying heat.

[0025] Although both tumble dryers and drying cabinets are equipped with fans, one can also arrange a fan in front of the air heater or between this and the drying equipments to ensure a good flow to these. The hot air temperature can also be regulated by the fan within certain limits. It can also be of advantage to arrange an inlet filter in front of the heat exchanger.

[0026] In many cases, laundry and drying spaces are so arranged in relation to the connection of the district heating to the heat exchangers for radiator water and tap water so that also the hot air exchanger can be arranged in the same place, so that compact and safe hot water installation can be achieved for the connection of the district heating. If the distance is too large, it is conceivable to arrange an intermediate heat exchanger between the primary water and that fed to the hot air exchanger.

[0027] If desired, one could imagine to use the outgoing and moist air (after filtering) from the drying cabinet or tumble dryer to heat a sauna. At this the temperature may be increased by the addition of hot air directly from the hot air heater.

[0028] By using relatively simple electrical or electronic logic the hot air generation can be adapted or respectively be switched on and off depending on the degree of utilization of connected drying devices.

[0029] Most existing tumble dryers (which are not of condenser type) as well as most already existing drying cabinets can fairly easily be incorporated in the above system, possibly with a disconnecting or removal of the electrical heating.

[0030] In particular, for apartment buildings and launderers the invention can be expected to be a good solution since they can negotiate for a good energy rate, which in turn can generate economic possibility for the installation of an extra meter only for the drying energy.

[0031] In many places district heating is combined with waste incineration, resulting in both an efficient and eco-friendly way to take care of garbage and an effective way to utilize the generated heat that can be distributed with a district heating network.

[0032] One problem with the utilization of heat from waste incineration is however the total efficiency in the system, since waste generation essentially is constant over the year while the heating demand essentially exists only for less than half the year. Much of the heat generated from the waste incineration will thus be unused and is thus vented away directly to the surrounding which means heating of the outside air. Storing waste is an opportunity for certain types of waste, but not all, and storage spaces are both space demanding and costly.

[0033] By in accordance with the invention utilize district heat for drying, the heat from the waste incineration will in the summer be better utilized and the corresponding electricity need not to be used be wasted, i.e. a considerable gain for the environment is obtained in addition to the economic gain.

Claims

1. Method for utilization of district heat energy, characterized by connecting drying devices for laundry to the district heating network.

2. Arrangement for drying laundry, characterized in that it include a heat exchanger connected to the district heating, said heat exchanger heating air which is then fed to one or several drying devices.

3. Arrangement according to claim 2, characterized in that the water in the district heating network flows through the heat exchanger.

4. Arrangement according to claim 2 or 3, characterized in that the drying devices are drying cabinets or tumble dryers.

5. Method according to claim 1, characterized in that the energy used for drying is measured separately.

6. Drying cabinet, characterized in that it is equipped with a high-temperature water heater for connection to a district heating network.

7. Drying drying cabinet, characterized in that it is connected to a circulating loop for hot tap water.

8. Arrangement according to claim 2, characterized in that dampers or the like are arranged for connected drying devices, for hot air cut off and / or for controlling a mixture of hot air and ambient air for temperature control.

9. Arrangement according to any of the claims 2-6 or 8, characterized in that it includes a return tubing for air from the drying device or drying devices.

10. Arrangement according to claim 9, characterized in that the drying devices are fitted with dampers for diluting the hot air with ambient air when a lower temperature is desired.

11. Arrangement according to any of the claims 2-4 or 8-10, characterized in that a heat exchanger is arranged to use room air or outside air to cool outlet drying air from drying cabinet or tumble dryer in front of the heat exchanger or air heater for transfer of the energy of warm water to the air from the cabinet before this returned to the cabinet, so that the cooling provides a drying of air from drying cabinet or tumble dryer before it is heated again.

12. Arrangement according to claim 11, characterized in that from drying cabinet or tumble dryer coming air is mixed with cooling air from the heat exchanger and delivered to the environment with a fan.

13. Arrangement according to claim 11 or 12, characterized in that an inlet for ambient air is arranged into the circulation loop for the drying air, for instance after the heat exchanger for condensation and in front of the air heater.

Drawing