HEAT EXCHANGER

Abstract: In a heat exchanger of the kind used for the transfer of heat from exhaust air, e.g. from rooms, to fresh air to be led into rooms, or for the transfer of heat the opposite way, means (9) for the cooled exhaust air are arranged after the outlet (4) with a view to transferring heat from the exhaust air to a heat reservoir (12), i.e. a heat pump circuit (10, 11). The thermodynamic efficiency is dependent on the difference in temperature, of course, and by transferring heat from exhaust air to for instance a water tank for hot water, the temperature being in some places close to the flow temperature of tap water, it will be possible to make use of much more of the latent heat of the exhaust air.

Description: HEAT EXCHANGER The invention relates to a heat exchanger of the kind used for the transfer of exhaust air, e.g. from rooms, into fresh air to be supplied to rooms, or the transfer of heat the opposite way. By such heat exchangers it has hitherto been technically and financially impossible to transfer all the thermal energy available. Consequently, the exhaust air after the heat exchanger is not cooled to the temperature of fresh air which will around the year on the average be colder than the exhaust air. The residual energy in the exhaust air after the heat exchanger is on the average on the order of 20--i0fa of the thermal energy available. The object of the ' invention is to make use of the residual energy. The heat exchanger is characteristic in that after the outlet of the cooled exhaust air there are means for the transfer of heat from the exhaust air to a heat reservoir, and in that the means comprise a heat pump circuit. In this way one can in a simple way improve the efficiency of two installations which are likely to be installed in the houses of the future, viz. firstly a mechanical ventilat- ion plant and secondly arrangements for the heating of water, e.g. tap water and water for central heating systems which are already existing in most houses. So, a preferred embodiment is characteristic in that the evaporator of the heat pump circuit is placed after the outlet of the exhaust air p.assing the heat exchanger, and in that the connected condenser is in heat conducting connection with the water in a water tank which is the heat reservoir. In this connection it is pointed out that the means for the transfer of heat from the exhaust air to the heat reservoir might comprise several stages, and as a first stage a heat exchanger for instance. According to the invention the water tank may be a reserv¬ oir for tap water. Usually the water flowing into such a tank is rather cold_, and, therefore, in placing the condenser properly good efficiency of the heat pump circuit is achievable. Further, according to the invention the water tank may be supplied with a heat exchanger intended to remove heat from the tap water. This is a simple way of contributing to the heating of a house. In order to permit easy defrosting of the evaporator, the heat exchanger according to the invention may have means for switching off the supply of fresh air and, if desired, for stopping the heat pump at the same time. According to the invention these may be adopted to switch¬ ing off and connecting on demand. Consequently the de¬ frosting can take place automically. A development of the heat exchanger is characteristic in that after the outlet for fresh air a further evaporator is arranged which is connected to the water tank in the same way as the evaporator after the outlet for exhaust air. Thus, a heat exchanger is pointed to which is in summer 1 operating an air-conditioning plant and at the same time contributing to the heating of water. An advantageous embodiment of this is characteristic in 5 that both evaporators are connected to the same heat pump circuit through barriers and leaving the option of one or the other evaporator being connected to the circuit. In this way only one circuit is required, which is connected to one or the other evaporator as required dependent on 10 whether summer or winter operation is required. The heat exchanger may be characteristic in that it consists of preferably square plates the edges of which are bent into a right angle and which edges are adhered. 1 . 5 This points to a very simple construction which is cheap in production. Further, the heat exchanger may be characteristic in being adopted to letting the (warmer) exhaust air pass one time 20 and in being adopted to letting the (colder) suction air pass one time through one half of the plates and then one time through the other half of the plates. In this con¬ struction the flow is turned by the (colder) suction air after the first passage of one half of the heat exchanger 25 making the air -flow back- through the other half of the heat exchanger in the direction opposite to that of the first flow. This construction has turned out to be extrem¬ ely fit for heat exchangers for air ventilating plants to be used in houses in winter. It has turned out that the 30 pressure drops thus occurring and in applying at the same time the heat pump circuit according to the invention will be completely identical at the temperatures prevailing. This means that the same fans with motors are applicable for the two air flows resulting in advantageous rational- 35 ization of production. The efficiency of the heat exchang¬ er may be very high as it has turned out that with a con- struction according to the invention it is possible to cool down the air led into the atmosphere to a temperature only two degrees (centrigrade) above the temperature of the atmosphere. The energy necessary to run the heat exchanger is used for heating, of course. Finally, the heat exchanger may be characteristic in that after the outlet from one half of the plates a heater is arranged. In a simple way this compensates for the loss of efficiency arising due to the heating of the cold air to room temperature. The invention is explained with reference to the drawing where fig. 1 schematically shows an embodiment of a heat exchanger according to the invention, fig. 2 a development according to the invention, fig. 3 an embodiment of a heat exchanger according to the invention built together with a heat pump system and a hot-water tank into a box-shaped unit schematically seen from in front and one front plate having been removed, fig. - a section along the line IV-IV of fig. 3, fig. 5 a section along the line V-V of fig. 3 "BUREAU OMPI fig. 's 6, 7, and 8 a so-called "exploded" view of fig. 9 shows part of a plate heat - exchanger of which fig.'s 6, 7, and 8 show the three lower plates, fig. 8 showing the bottom one, fig. 7 the bottom plate but one, and fig. 6 the third from the bottom. In fig. 1 is shown a box-shaped unit 1 containing a so- called cross-flow heat exchanger 2 for air and two fans 2 and -4. The fan 3 sucks fresh air from an inlet 5 through the heat exchanger 2 and blows it out through an outlet 6, whereas the fan -4 sucks exhaust air from a room from another inlet 7 through the heat exchanger 2 and blows it out through an outlet 8. In the outlet 8 an evaporator 9 is arranged forming part of a heat pump circuit consisting of a compressor 10 and a condenser coil 11 arranged in a water tank 12 with an inlet 13 and an outlet 1-4. Often, the tank 12 will be placed at some distance from the other elements of the constructions, and in that case the pipes will be insulated. Now, the heat exchanger operates in the following manner provided that the fresh air is colder than the exhaust air which will be the case in winter. The exhaust air sucked in through the inlet 7 will liberate heat in the cross-flow heat exchanger 2, which is in part, i.e. with a certain efficiency, transferred to the fresh air sucked in through the inlet 5. The heated fresh air is blown through the outlet 6 to rooms not shown whereas the cooled exhaust air is led through the outlet 8 for further cool- ing when passing the evaporator 9 before being led into the open air. The heat removed by the evaporator 9 is by the compressor 10 pumped into the tank 12 where it will through the condenser coil 11 liberate into the water preferably in the coldest water at the bottom and near the inlet 13. Fig. 2 ' shows a development of the heat exchanger according to fig. 1 and where the elements of the construction shown again carry the same reference numbers. The differ¬ ence consists in a further evaporator 15 having been built into the outlet 6 connected parallelly to the other evap¬ orator 9 and valves 16 and 17 being arranged in the heat pump circuit making it possible to switch on one evapor¬ ator or the other. In case of the outdoor temperature being higher than that of the rooms to be supplied with fresh air, and the evaporator 15 being on, it will be possible to cool the fresh air before it is led into the rooms, and at the same time the water in the tank 12 is heated. The heat exchanging in the cross-flow heat exchanger 2 will in that case be in the opposite direction. In both cases the heat collected by evaporators 9 and 15 is the heat not transformed in the cross-flow heat exchang¬ er 2 as its efficiency will never be 1005?. Around the tank may be arranged a jacket 18 with an access 19 and an exit 20.The heat exchanger thus establ¬ ished is applicable for heating. Fig.'s 3, , and 5 are to be look upon in combination, and the items of these three figures carry the same ref¬ erence numbers. Fig. 3 shows a unit in which a hot water tank 21 is arr¬ anged. Above the tank a box-shaped plate heat exchanger 22 of square section is arranged on its edge. The hot water tank 21 and the plate heat exchanger 22 are inter-connect¬ ed by a heat pump system consisting of a heat pump 23 and I U EΛTΓ O PI y->. 1P0 y$ y&RKAΥ\ aa evaporator 2-4 arranged along one of the fan sides 25 in the heat exchanger. Along the same side cooled air from the room is flowing, the air being let in through the opposite, rectangular side 26, see arrow 27 in fig. 3 and arrow 28 in fig. 3 and 5. The air is supplied by a fan 29 which is connected with a room in a house. When passing through the heat exchanger 22 and the evaporator 24 the air is cooled to a temperature which will often be only a couple of degrees above temperature of atmos- phere. After the evaporator 2-4 the air is led into the atmosphere as shown by arrows 30, 31, and 32. Fresh atmospheric air is taken in through an inlet 33 and led through a fan 34 towards one half 35 of the side 36 of the heat exchanger 22 at which side 36 a triangular screen 37 is arranged. In order to clearly show the pos¬ ition of the triangular screen 37 its sides carry the references a, b, and c in the three figures. When the fresh air has flown through half of the heat exchanger 22 it will reach the room 38 which is a closed room. From there it is pressed through the other half of the heat exchanger as shown by dotted arrow 39, and the air will come out on the other side of the triangular plate 37, thus. In this room heating elements - not shown for the sake of clearliness -• are arranged. The air is led into the room of the house through the outlet 4l. Fig. 6 shows a square plate 41 having two upward bent edges 42 and 43 opposite each other, and two downward bent edges 44 and 45. Fig. 7 shows the same but rotated 90 and the two upward bent edges 46 and 47 being intend¬ ed for adhesion to the edges 44 and 45 respectively. Adhesion according to this principle makes it possible to build a plate heat exchanger as shown in fig. 9 and applicable in the construction according to fig.'s 3, 4, and 5- The invention is widely variable. Thus, it is clear that in principle the cross-flow heat exchanger 2 may be a heat exchanger of any kind. For the sake of clearliness, no throttles are shown in the heat pump and cooling circuits shown, but of course there are such throttles.

Claims: C L A I M S 1. Heat exchanger of the kind used for transfer of heat from exhaust air, e.g. from rooms, to fresh air to be led into rooms, or transfer of heat the opposite way, c h a r¬ a c t e r i s t i c i n that after the outlet for cooled exhaust air there are means for transfer of heat from exhaust air to a heat reservoir and in that these means comprises a heat pump circuit. 2. Heat exchanger according to claim 1, c h a r a c t- e r i s t i c i n that the evaporator connected to the heat pump circuit is arranged after the outlet for the exhaust air passed through the heat exchanger and in that the condenser is conductively in connection with the water in a water tank which is the heat reservoir. 3. Heat exchanger according to claim 2, c h a r a c t¬ e r i s t i c i n that the water tank is a reservoir for tap water. 4. Heat exchanger according to claim 3, c h a r a c t ¬ e r i s t i c i n that the water tank is supplied with a heat exchanger intended to remove heat from the tap water. 5. Heat exchanger according to claims 2, 3, or 4, c h a r a c t e r i s t i c i n means for switching off the supply of frehs air and, if desired, for stopping the heat pump at the same time. 6. Heat exchanger according to claim 5, c h a r a c t¬ e r i s t i c i n that the means are adopted to switching off and connecting on demand. 7. Heat exchanger according to one or several of claims 2-6, c h a r a c t e r i s t i c i n that after the outlet for fresh air a further evaporator is which is connected to the water tank in the same way as the evaporator after the outlet for exhaust air. 8. Heat exchanger according to claim 7, c h a r a c t- e r i s t i c i n that both evaporators are connected to the same heat pump circuit through barriers and leaving the option of one or the other evaporator being connected to the circuit. 9. Heat exchanger according to claim 1, 2 or 3 3 c h a r¬ a c t e r i s t i c i n that it consists of plates. 10. Heat exchanger according to claim 9, c h a r a c t¬ e r i s t i c in the plates being preferably square the edges of which are bent into a right angle and which edges are adhered. 11. Heat exchanger according to claim 9 or 10, c h a r¬ a c t e r i s t i c in that it is adopted to letting the (hot) exhaust air pass one time and in that it is adopted to letting the (colder) suction air pass one time through one half of the plates and then through the other half of the plates one time. 12. Heat exchanger according to claim 11, c h a r a c t¬ e r i s t i c i n that a heating element is arranged after the outlet from the other half of the plates. llU EΛf OMPl ^£RN1T\

Inventors: SVENDSEN B
Applicants: GENVEX ENERGITEKNIK AS, SVENDSEN B
Application year: 1980
Main classification: F24J3
IPC codes: F24D11, F24F5, F24F12, F28D9