GB2077852A

GB2077852A - A Heating Plant Comprising a Heat Pump

Info

Publication number: GB2077852A
Application number: GB8101927A
Authority: GB
Original assignee: Motorenfabrik Hatz GmbH and Co KG
Current assignee: Motorenfabrik Hatz GmbH and Co KG
Priority date: 1980-06-11
Filing date: 1981-01-22
Publication date: 1981-12-23
Also published as: FR2484540A1; DE3021824A1; IT1136716B; IT8122257A0; JPS5714134A

Abstract

A heating plant, for example for a domestic water heating system, comprises a compressor 10 which is operated by an internal combustion engine 12 with a housing which is devised to accommodate a heat exchanger 28 which utilises waste heat from the engine to heat the water or other medium circulating in the system. The housing of the heat exchanger may be combined structurally with the engine cylinder head (as shown) or with another part of the engine, e.g. the crank case. The waste heat may be taken from the engine cooling water or lubricating oil. <IMAGE>

Description

SPECIFICATION A Heating Plant Comprising a Heat Pump This invention relates to a heating plant comprising a heat pump with a compressor driven by an internal combustion engine, and means for transferring waste heat from the internal combustion engine through at least one heat exchanger to a heat carrier medium in the heating circuit of the plant.

In known plants of this kind the heat exchanger is an independent separate constructional part and is connected through freely-disposed conduits with the heating circuit and the housing part of the internal combustion engine at which the waste heat is transmitted. Since heating plants are often automatically switched on and off, mostly hourly, special expansion compensators (for example resilient undulating pipes) have to be installed, particularly in the conduitry between the internal combustion engine and the heat exchanger, to cater for multiple changes between thermal expansion and contraction in the conduitry system. In addition a plurality of junction points are necessary in the connections between the internal combustion engine and the heating circuit.

Plants of this nature therefore have a number of deficiencies. First then the cost of the expansion compensators is expensive and their life limited. Moreover the many connection points have to be sealed very carefully so that the environments of the plants, mostly cellars of households, are not polluted by media escaping from the heating circuit or the internal combustion engine. Finally the maintenance and cleaning of the heat exchanger itself is very troublesome and expensive, because many conduits have to be taken down and later connected up again.

It is an object of the present invention to obviate these difficulties of known plants. This is achieved in the present invention by the fact that the internal combustion engine has a housing which is devised, at a part thereof at which the aste heat is transmitted, to receive heat exchanger.

This arrangement in accordance with the inventim caters for the installation of a heating plant requiring a minimum of free-lying conduits between the heating circuit and the internal combustion engine. The lost heat which occurs at the housing part of the internal combustion engine is in practice conkcted in a major measure to the heat exchanger installed in the same part of the housing, meaning a high degree of efficiency of the heat exchanger. No freelying connection point or junction points, or expansion compensators, are needed between the internal combustion engine and the heat exchanger so that in addition there is an economical structure and more congenial operation.

In presently available heating plants of the kind here concerned the waste heat of the internal combustion engine is frequently regarded as lost heat and is transferred through the heat exchanger to the heat carrier medium in the heating circuit. In this connection in accordance with a further advantageous feature of the present invention a cylinder head of the internal combustion engine having a waste gas discharge conduit, and a receptacle for the heat exchanger are combined to form a unitary part of the housing, whereby the exhaust gases from the internal combustion engine are conducted from the exhaust conduit directly to the heat exchanger mounted in the same part of the housing and only then leave after flowing through the cylinder head.

In a simple construction using the principle of the present invention the cylinder head of the internal combustion engine is provided with at least one channel which surrounds the heat exchanger and through which the heat carrier medium is conducted from the heating circuit and thus flows around the heat exchanger through which flow the waste gases. A construction of this nature can be used independently of the type of medium which is used as a heat carrier in the heating circuit and also of the type of internal combustion engine used for operating the system.

From this it follows that an air-cooled internal combustion engine mav be used.

A further particularly advantageous form of the invention is found in the case of plants using water as the heat carrier medium and watercooled internal combustion engines. In such a case the cylinder head of the internal combustion engine is provided with at least one channel surrounding the heat exchanger through which the exhaust gases from the engine pass, the water cooling the engine being conducted through this channel and thereby flowing around the heat exchanger, the water heated after flowing around the heat exchanger being conducted to the heating circuit of the system.

A useful constructional development of the invention resides in an arrangement in which the heat exchanger is a closed unit arranged so as to be replaceable from the exterior in the receptacle provided in the cylinder head of the internal combustion engine. With this construction any dismantling and reinstallation of the heat exchanger for the purpose of cleaning or maintenance can be carried out very easily.

Embodiments of the invention are described below with reference to the accompanying drawings, in which: Figure 1 is a alagrammatic illustration of a heat pump and compressor and an internal combustion engine operating the same.

Figure 2 is an enlarged view, with part in vertical longitudinal cross section through the cylinder and cylinder head of the internal combustion engine.

Figure 3 is a horizontal cross section through the cylinder head taken on the line A-A of Figure 2, and Figure 4 is a vertical cross-section through the cylinder head taken along the line B-B of Figure 3.

The heat pump which is diagrammatically illustrated in Figure 1 includes a two-cylinder compressor 10 for a liquid coolant medium in the circuit thereof. The driving shaft 1 Oa of the compressor 10 is operated by the driving shaft, that is to say the crankshaft, 1 2a of a watercooled internal combustion engine 12 of known form, for example a single-cylinder injection engine. The liquid coolant medium at a temperature of about 20C is evaporated in an evaporator 14 upstream of the compressor 10, the liquid - as indicated by arrow E - absorbing heat from an ambient medium for example subsoil water or air, and evaporating. The coolant medium vapour is then passed to the compressor 10 through a suction pipe 1 6.

During the compression phase the coolant medium vapour is concentrated, thereby heated up, and thereafter conducted through a conduit 1 8 to a condenser 20. The coolant medium vapour which is heated in compressor 10 to about 600C flows through a conduit 20a in the condenser 20 and thereby releases the major portion of its heat and liquifies again. The liquified coolant medium is conducted through an expansion valve 26, expands and reassumes its original temperature of about 20C. It then flows back to the evaporator 14 to begin a new circuit in the heat pump.

The used, cold water from a heating plant, for example a domestic heating system 24 is passed through a separate conduit 22 of the condenser 20 and absorbs the heat released by the coolant medium. The water heated after passing through the condenser 20 is conducted to the internal combustion engine 12 at a joint 1 2b and delivered for cooling this engine into the cooling system thereof, which is indicated in dotted lines only. At the end of this cooling circulation the heated water is conducted through an additional heat exchanger 28 and further heated again with the assistance of the lost heat engendered from the exhaust combustion gases.The superheated water is then conducted to another joint 1 2c on the engine 1 2 to leave its cooling circulation system at this point The superheated water is conducted into the domestic heating plant 24 through a conduit 30, and this plant forwards the major proportion of the heat obtained in the direction indicated by the arrow H for house heating purposes.

The details of the cooling system of the engine 12 and the additional heat exchanger 28, only diagrammatically illustrated in Figure 1, are set forth in the ensuing description and the further figures. The cylinder -- and cylinder head arrangement of the engine 12 are here illustrated in section. The cylinder 32 accommodates an upright cylinder bush 34 housing a piston 36. A connecting rod 38 coupled to the piston is engaged with the crankshaft 1 2a of the engine 12 in a manner known per se. Fastened to the cylinder 32 by four screw bolts 40 is a cylinder head 42 in which is arranged, in the normal way, a suction valve 44, an exhaust valve 46, and a fuel injection nozzle 48. Each valve is operated through an associated valve rocker 50 which is controlled from an operating drive (not shown) by a thrust rod 52 likewise in known fashion.A cylinder head cover 44 closes the two valve rockers 50 from the exterior. Combustion air is conducted to the suction valve 44 through a duct 42a, whilst the waste gas passing out through the exhaust valve 66 is passed through the exhaust duct 42b.

The operation of a four-stroke injection combustion engine of the kind described is known and need not therefore be further described in detail.

Provided between the parts 32 and 34 of the engine housing is a narrow annular space 56 which is connected to the water joint 1 2a previously mentioned, which latter is arranged at the lower area of the housing 32, 34. The cylinder 32 is provided with two lateral flanges 32f in each of which is a duct 60 and there is a flow connection between each of these ducts and the annular space 56 through a transverse duct 58.

To cool the piston cylinder housing 32, 34 and the cylinder head 42 the water passes upwards into the space 56, ducts 60 and through openings 42d in the head into the cooling channels 42k in the cylinder head 42.

The cylinder head 42 is constructed so as to accommodate the heat exchanger 28. An elongated channel 42t extending longitudinally at right angles to the axis of the cylinder is defined by tubular walls 42w of the head 42 and made as an integral housing unit with the head 42 through intermediate walls 42z. A connecting channel 42v defined between the walls 42w and 42z runs parallel to the channel 42t. The channel 42v is in communication with the cooling channel 42k through a conduit-forming perforation 42s passing beneath the exhaust channel 42b, so that water can flow from the cooling circulation system in the cylinder head 42 into the connecting conduit 42vand through the opening 42 vv thereof into the annular channel 42t.

The tubular walling 42w of the head 42 is provided at its two ends with annular flanges 42f mounting the heat exchanger 28. This comprises a plurality of thin small diameter pipes 28a which are held together at their ends by two retaining plates 28b. The heat exchanger 28 can be introduced as a closed unit into the mounting flanges 42f through a lateral opening 42c in the cylinder head 42, this opening being closable by a cover 62. In contrast the waste gas exhaust conduit 42b of the head 42 opens into a chamber 42bb between the opening 42f and the cover 62 so that the hot combustion exhaust gas passing out through the exhaust valve 46 can flow from the chamber 42bob through the interior of the small thin heat exchanger pipes 28a and leave the same at the other end thereby to pass to a suitable exhaust point through an exhaust pipe 64.

During their passage through the heat exchanger 28, that is to say the pipes 28a thereof, the waste gases outflowing from the cylinder at a temperature of about 4000C give up a major part of their heat, which represents heat lost during the combustion process, to the water surrounding the small pipes 28a, so that the waste gases at the exhaust pipe 64 have a temperature of only about 1 500C. The water super-heated by the waste gases passes from the channel 62t through an opening 42tt and is conducted through the connecting pipe 1 2c to the household heating system 24 to give up its heat in this system in the known way.

The advantages arising from the construction of the cylinder head 42 for simultaneous accommodation of the heat exchanger 28 have already been detailed at the beginning hereof. It need only be added to this that -- deviating from the embodiment described -- it is possible to use a common housing unit for the cylinder head and the heat exchanger even where the heat carrier circulating in the heating plant and the coolant for the internal combustion engine is not the same (water). Apart from this the additional heat exchanger (28) couid be made as a single unit with a part of the engine housing other than the cylinder head if it is appropriate in the case of specific internal combustion engines to absorb the lost heat at a part other than the cylinder head and to be passed there into the additional heat exchanger. it would be feasible forsxample to construct the crank case of the internal combustion engine simultanbusly as a heat exchanger receptacle if the lost heat of the hot lubricating oil there stored is to be conducted through the heat exchanger to the hot water or other medium in the household heating system.

Claims

1. A heating plant comprising a heat pump with a compressor driven by an internal combustion engine, and means for transferring waste heat from the internal combustion engine through at least one heat exchanger to a heat carrier medium in the heating circuit of the plant, characterised by the fact that the internal combustion engine has a housing which is devised, at a part thereof at which the waste heat is transmitted, to accommodate the heat exchanger.

2. A plant according to Claim 1, in which the waste heat referred to is represented by the exhaust heat of the internal combustion engine, characterised by the fact that a cylinder head of the internal combustion engine, having a wastevas discharge conduit, and a receptacle for the heat exchanger are combined to form a unitary part of the housing, whereby the exhaust gases from the internal combustion engine are conducted from the exhaust conduit directly to the heat exchanger mounted in the same part of the housing and only then leave after flowing through the cylinder head.

3. A plant according to Claim 2, characterised by the fact that the cylinder head of the internal combustion engine is provided with at least one channel which surrounds the heat exchanger and through which the heat carrier medium is conducted from the heating circuit and thus flows around the heat exchanger through which flow the waste gases.

4. A plant according to Claim 2 wherein water is the heat carrier medium in the heating circuit, and the internal combustion engine is watercooled, characterised by the fact that the cylinder head of the internal combustion engine is provided with at least one channel surrounding the heat exchangerhhrough which the exhaust gases from the engine pass, the water cooling the engine being conducted through this channel and thereby flowing around the heat exchanger, the water heated after flowing around the heat exchanger being conducted to the heating circuit of the system.

5. A plant according to Claim 2, characterised by the fact that the heat exchanger is a closed unit arranged so as to be replaceable from the exterior, in thececeptacle associated with the cylinder head of the internal combustion engine.

6. A plant according to Claim 6, characterised by the fact that the exchanger comprises a plurality of parallel tubes which are combined together at their open ends in circular holders, and a mounting opening for each holder is provided in the receptacle associated with the cylinder head of the internal combustion engine and theholder sits in sealed fashion in this opening.

7. A heating plant substantially as herein described and as shown in the accompanying drawings.