A DEVICE FOR PREPARING HOT WATER BY MEANS OF AN EXTERNAL HEATI SOURCE

The present invention refers to a device for preparing hot wat in a water heater by means of an external heating source, e. at least one solar collector, which device incorporates a he exchanger consisting of an internal circulation system for heat water and an external circulation, system for the solar collect heat medium.

BACKGROUND OF THE INVENTION

Preparation of hot water by means of an external heating sour may be subdivided into three different systems.

According to a first system, cold water is allowed to -flow fr the bottom of the heater into a heat exchanger provided outsi the heater and the water heated therein is thereupon supplied the upper part of the heater. This system has the advantage th most conventional water reservoirs may be used. A high operati temperature in the solar collector however results in l efficiency and the system is difficult to adjust with a mai tained high peak temperature in the water reservoir.

According to a second system is used a particularly shap double-walled heater. In this case the heater serves as a he exchanger. Also this system is difficult to adjust with a mai tained high peak temperature in the heater. This system of cour will be expensive to manufacture and the system requires a b volume of water in the solar collector circuit.

In the third system a heat exchanger is arranged inside the low part of the heater. This system is easy to adjust and it gives good efficiency at low solar collector temperature. The syst however requires a particularly designed heater, which i expensive and the location of the heat exchanger in the heate

makes maintenance and repair more difficult.

PURPOSE AND MOST ESSENTIAL FEATURES OF THE INVENTION

The purpose of the invention is to provide a hot water heater which does not suffer from the drawbacks mentioned above an which can furthermore be manufactured at a particularly low cost i.a. in that conventional, e.g. existing hot water heaters an conventional heat exchangers which are only slightly modified ca be utilized. These tasks have been solved in that the hea exchanger is situated outside the heater and only connected t this via the cold water inlet by means of one end of an intak pipe, the opposite end of which is connectable to a cold wate conduit, that to the intake pipe is connected the inlet as wel as the outlet conduit of the internal circulation system, whereb the outlet conduit is arranged to extend with play through on end portion of the intake conduit and via the cold water intak into the heater, and that the cold water intake is arranged as a outlet for the heating water for the heat exchanger.

DESCRIPTION OF THE DRAWINGS

The invention hereinafter will be further described wit reference embodiments shown in the accompanying drawings.

Fig. 1 shows diagramatically the device according to th invention connected in a solar collector system.

Fig. 2 shows in a perspective view the heat exchanger of th device. Fig. 3 and 4 show in cross sections modified embodiments of th heat exchanger.

DESCRIPTION OF EMBODIMENTS

The device shown in Fig. 1 for heating hot water incorporates heat emitting unit in the form of a solar collector 1, whic

preferably operates with a fluid as heat transfer medium. T solar collector is, via an intake conduit 2a connected to i lower part and via an outlet conduit 2b connected to its upp part, connected to a heat exchanger 3. According to the inventi this is situated outside the heater, from which the hot water c be taken out.

A circulation pump 5 is provided in the external circulati circuit 15 of the heat exchanger 3 in order to circulate the he medium between this and the solar collector 1. The heater which is of conventional type, has at its lower part a central disposed cold water intake 6 and a feeding conduit 7 at the upp part of the reservoir, through which hot water can be drawn o via a water tap 8 or the like.

When installing the solar collector 1 and its heat exchanger 3 a hot water heater 4, the cold water conduit 16 is disconnect from the cold water intake 6 by removing the pipe coupling 17 The heat exchanger 3 of the solar collector consists of a bran pipe 18, which is preferably centrally located, and which has t same outer dimension as the cold water intake 6 and which b means of the coupling 17, which can be a clamping coupling, ca be connected to the cold water intake 6. The internal circula tion circuit 19 is connected to the branch pipe 18, and consist of a helically wound pipe conduit 9, the inlet end of which, vi a connecting conduit 10 is connected to the lower part of th branch pipe 18, whereas the outlet end of the pipe conduit 9 wit a connecting conduit 11 is connected to the upper part of th branch pipe 18, thus that the connecting conduit 11 passes i water-proof manner through the branch conduit and extends axiall out from the tube end so far that the nozzle of the connectin conduit will be located in the upper part of the heater 4. Th connecting circuit 11a thus forms the outlet conduit of th internal circulation system 19, which has so much smalle diameter than the branch pipe 18 and the extension thereof, i.e the cold water intake 6, that this forms an outlet for coole

f

heater water, which can flow down through through the branc pipe 18 and into the connecting conduit 10 of the interna circulation system 19. Below this the branch pipe 18 is designe thus that the cold water pipe 16, which is disconnected from th hot water heater 4, can be connected via a pipe coupling 17.

In the embodiment shown in Fig. 2 the heat exchanger 3 mainl consists of a smooth, oval external tube 9, and an internal finned tube 12, which forms a continuation of the conduits 2a an 2b. This finned tube 12 has an external diameter, smaller tha the internal diameter of the outer tube, thus that a water-fille space is formed between the outer tube 9 and the finned tube 12.

The above described device operates thus, that cooled, cold wate flows from the heater 4 through the outlet opening and the intak pipe 18 via the connecting conduit 10 to the external tube 9 o the internal circulation system 19. As soon as the heat emittin fluid from the external circulation system 15 has • a highe temperature than the water in the lower part of the heater 4, th water - due to the thermosiphon effect - will come in motion. Th heated water in the external tube 9 raises to the upper part o heater 4 through the conduit 11a, and the more cold water flow down in the intake pipe 18 and back to the external tube 9 Concurrently with the removal of water from the heater 4 col water is gradually supplied from the cold water conduit 1 through the intake pipe 18, which cold water raises partl through the opening 13, but also through the the conduits 10, and 11 to the heater 4. Due to differences in density, i.e. du to the stratification ^" of the water in the heater 4, the more col water will occupy the lower part thereof.

Due to appropriate dimensioning of the intake pipe 18 and th conduit 11a overheating in the heat exchanger is effectivel prevented at the same time as the heated water obtains such lifting power, that normally no circulation pump is required i the internal heat receiving circulation circuit 19.

In the embodiment shown in the heater 4 will occure an upp water layer of high temperature and a lower water layer gradually decreasing water temperature. By varying the length which the conduit 11a extends up into the heater 4 it is possib to adjust the extension of these layers.

If the hot water heater 4 is of conventional type it is provid with one or more immersion heaters, which can emit energy wh the energy from the solar collector is not sufficient. T provision of the heat exchanger below the water reservoir resul in a simple and space-saving arrangement, without any inte ferences whatsoever in the heater, which means that almost a existing hot water heaters can be furnished with the devi according to the invention and during spring, summer and fa obtain an essential part of its hot water need by solar heat.

An essential advantage is that the heat exchanger can not co the water of the water reservoir, as the supply of heated wat only takes place under utilization of the thermosiphon effect. temperature reduction during night when the circulation medium the solar collector may get a considerably lower temperature th the heater water, therefore involves no cooling thereof as t thermosiphon effect terminates even if the circulation pump should be running.

Fig. 3 shows a variant of the heat exchanger according to t invention. This differs from the embodiment described above i that the heat exchanger coil 12 is arranged in a heat exchange container, corresponding to the external tube 9. The hea exchanger coil 12 is arranged around the centrum intake pipe 18 This is at the lower side closed in front of the cold water inle 18a and it is equipped with inlets 14, formed as latera openings. The space between the external casing 9 and the intak tube 18 communicate in the upper part of the heat exchanger wit the conduit 11a, which in the same manner as in the precedin

embodiment passes through the opening 13 of the intake pipe 18 and extends a distance into the heater 4.

The embodiment according to Fig. 4 differs from the abov embodiments in that the internal circulation conduit 9 of th heat exchanger 3, which is helical, externally is in hea transferring connection with the external circulation conduit 12, which is also helical, and which is preferably soldered to th outside of the pipe 9. In this manner is obtained an unexpensiv and efficient heat exchanger, which without problems can take u the rather big thermal motions to which it is subjected. A hea insulation is designated 20.

The new device is easy to adjust. It gives a good efficiency als at low solar collector temperature and it can be used togethe with most water reservoirs available on the market, which means that the cost for the water reservoir generally need not be cal culated into the price of the plant. It furthermore is easy t connect to existing hot water tap systems. It of course i possible to use a heat exchanger of mainly conventional design.

The arrangement of the rather coarse intake pipe 18 and th smaller hot water pipe 11, 11a arranged to extend therethroug solves the technical problem of maintaining a low temperature i the heat exchanger for obtaining a good efficiency of the sola collector and for avoiding a local boiling at the same time a water may pass into and out from the rather small outlet 13 fro the heater.