GB1589534A

GB1589534A - Powered heating unit

Info

Publication number: GB1589534A
Application number: GB30855/77A
Authority: GB
Original assignee: MOTORHEIZUNG GmbH
Current assignee: MOTORHEIZUNG GmbH
Priority date: 1976-07-28
Filing date: 1977-07-22
Publication date: 1981-05-13

Description

(54) POWERED HEATING UNIT (71) We, MOTORHEIZUNG GmbH., of 73 Bödekerstrasse, 3000 Hannover 1, Federal Republic of Germany, a Joint-Stock Company organised under the laws of the Federal Republic of Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to powered heating units, comprising heat pumps driven by combustion engines. The mode of operation of heat pumps is based on the fact that they extract heat from the environment and release this again in a space which is required to be heated.

Such powered heating units still have the disadvantage that the degree of energy utilization, that is to say the ratio "calefactory energy" to "primary energy" to be expected in producing it" of such installations has not yet been fully exhausted and the combustion engines and compressors employed have only a relatively short working life.

It is therefore an object of the invention to improve the degree of energy utilization of the conventional powered heating units and to provide a method of increasing the life of the combustion engines employed for powered heating units, especially the life of the diesel motors preferentially employed according to the invention. At the same time, the possibility should be given of increasing the life of the compressors of the heat pumps, since these are also relatively expensive to produce and also have only a limited life.

The invention consists in a powered heating unit comprising a combustion engine, a heat pump comprising a compressor driven by said combustion engine and a vaporizer, a heat transfer medium circulation system coupled to said compressor and vaporizer for providing heat to a heating system and means for feeding waste heat energy of said combustion engine into said heating system or into at least one further heating system, the combustion engine being arranged within a heat insulating housing, means being provided for regulating the throughput of the heat transfer medium in the heat transfer medium circulation system in dependency of the temperature of the envlronment of the vaporizer of the heat pump by controlling the speed of rotation of said combustion engine.

A powered heating unit of similar construction is disclosed in our Co-pending Divisional Application No. 10247/79 (Serial No. 1589535).

It will be appreciated that the combustion engine not only fulfils a drive function but also itself serves as a source of heat. The heat of combustion formed during combustion of the fuel may be fed, on the one hand via the engine block and an appropriate coolant and, on the other hand, via the combustion gaes, from the engine via heat exchange units to the appropriate heating system. The coolant used is preferably water, though other coolant fluids employed for combustion engines, or mixtures of such fluids, or gaseous coolants, can also be employed. The throughput of the preferably re-cycled liquid coolant depends on the working temperature of the combustion engine.

The hot combustion gases (exhaust gases) of the combustion engine can, as is known, also be used entirely or partially for heating absorbers or absorbers of an additional heat pump, which instead of the compressor possesses absorbers or adsorbers. This combination is admittedly relatively complicated but gives a very high degree of energy utilization, especially in sizable installations.

In the powered heating units according to the invention, the hot combustion gases may be brought into direct contact with heat exchangers, or the combustion gases may be passed into a fluid and the heat released to the fluid is transferred to a heat exchanger connected to the appropriate heating system.

Of course combinations are also possible, for example if the hot combustion gases first serve to heat the absorbers or adsorbers of the additional heat pump and only then come into contact with the heat exchangers, or are fed into the fluid. Preferably, the combustion gases are fed into water, which is contained in a heat- insulating vessel and serves as a wet exhaust gas heat exchanger.

The heat transferred to the water is then transferred directly to the heating system via appropriately designed heat exchangers. At the same time, a sound-damping action on the gases issuing from the combustion engine is achieved with this method. In addition, a purification of the combustion gases takes place, so that "clean" combustion gases, which do not cause any further pollution of the environment, issue from the chimney.

The cleaning action of the wash fluid can of course be further increased in an advantageous manner by chemical additives which are known to those skilled in the art. Quite apart from this, it should be noted at the present point that the engine, for example, a diesel engine, is not operated under maximum load, as a result of which alone the combustion gases are already substantially cleaner than in the case of an oil burner.

In order very substantially to utilize the heat of combustion generated by the combustion engine and optionally the heat released by the compressor, the combustion engine is surrounded, optionally the gearbox and the compressor also, with a heat-insulating housing. Preferably, the combustion engine is directly embedded in foam. Polyurethane foam is preferred as the encasing material. The exception to this encasing in foam are the heat-sensitive subsidiary units, such as for example, the starter and the dynamo, if these have not been replaced by a direct current supply. The embedding in foam is carried out so as to facilitate servicing, that is to say so that the parts of the housing which is directly foamed on to the motor can be removed in the places which must be accessible for servicing.To achieve this, for example, the combustion engine without the subsidiary units is placed in a mold which is sub-divided into individual zones by means of dividing sheets. Before being embedded in the foam, the combustion engine itself is spread with a release agent in the places from which the parts of the foamed housing are to be removed during servicing. By embedding the combustion engine in foam, substantially improved energy utilization of the energy contained in the fuels is achieved.Furthermore, the foaming results in a certain reduction of the noise when the combustion engine is running and in an improvement of the starting behaviour of the combustion engine as a result of the cooling not being excessively rapid, which offers interesting possibilities especially in the case of diesel engines, and which, once again, achieves a certain energy saving as a result of the reduced time for which the starter runs.

The automatic increase in operating temperature of the combustion engine, associated with the embedding in foam, is compensated by a correspondingly greater throughput of cooling medium, and at the same time an additional, controlled, removal of the heat of combustion, which is lead to the heating system, results.

Figure 1 shows, in a schematic representation and by way of example, a powered heating unit according to the invention. The total installation rests on a concrete foundation 17 which is mounted in a vibrationdamped and sound-damped manner on appropriate damping material 5. The diesel engine 15 arranged within a heat insulating housing (not shown) and mounted on vibration-damping hard rubber blocks 16 drives the compressor 2 of the heat pump via the gearbox 1. The compressor 2, like the diesel engine 15, is mounted on vibration-damping hard rubber.

The hot combustion gases of the diesel engines are passed, via the exhaust 14 and the non-return safetly valve 19, into the water of the wet exhaust gas heat exchanger 13, where they transfer their heat to the liquid mentioned. The cooled combustion gases are discharged through the chimney 12. The heat taken up in the wet exhaust gas heat exchanger 13 is fed via the heat exchanger connecting system, operated by the circulating pump 20, to the heat exchanger 3. The cooling heat produced in the diesel engine 15 during operation is also fed to the heat exchanger 3, via the "water pump" built into the diesel engine but not shown in the figure, with the aid of the cooling medium. The heat provided by the wet exhaust gas heat exchanger 13 and by the cooling system is fed to the space heaters 10 via the heating installation driven by the circulating pump 9.

In the heat pump circuit, working medium (e.g. CF2CI2) the pressure of which has, relatively, been let down, passes into the vaporizer 11 and is there vaporized by absorbing the heat of the invironment. This vapor is fed to the compressor 2 and is compressed by the latter almost adiabetically, in the course of which its temperature rises to about 550C. This hot vapor under pressure transfers its heat to the heat exchanger 4. As a result of the cooling effected in the heat exchanger 4, condensation to the liquid phase takes place. The working medium, which is still under pressure, then passes to the pressure let-down device 18 and from there back into the vaporizer 11.

The heat supplied to the heat exchanger 4 is fed by means of the pump 6 from the heat exchanger 4 to the spacer heaters 8.

It is true that using the measures described above an increase in the degree of energy. utilization is already achieved, but nevertheless, substantial heat losses still occur, attributable to the heating-up of the main units, for example the engine and the compressor. The same is true of heat pumps driven by electric motors, since these motors undergo a not insignificant rise in temperature during operation. Even the well heatinsulated heat exchangers can transfer small amounts of heat to their environment, in spite of their very low K value. This all means that the heat pumps, during operation, transfer a not insignificant proportion of heat, hereinafter referred to as "residual heat" to the environment.

Accordingly, in an embodiment of the invention, a heat pump is used in which the "residual heat" released by the main units is utilized almost completely. This is done by disposing the compressor and/or the engine, including the gearbox and/or possible subsidiary units belonging to the engine and/or to the compressor, and/or the heat exchanger, each under an additional, or a shared additional, bell-shaped vaporizer for the working medium, it being possible for one or more of the units located under the additional vaporizer or vaporizers to be heat-insulated.

The bell-shaped vaporizer preferably consists of a vaporizer unit which can be dismantled into individual vaporizers, and the vaporizer unit can also represent a genuine unit in respect of the flow of the working medium. Of course, it is also possible for the working medium to flow through the individual vaporizers in separate circuits. The ability to dismantle the vaporizer unit, which is preferred, is important for practical considerations, both in respect of assembly and in respect of possible partial dismantling in the case of repair work or servicing work on the units located under the additional vaporizer. As used herein, "bell-shaped vaporizer" means any vaporizer which, by virtue of its shape, makes it possible to surround the units from all sides, except for their base surface.The shape of the additional bell-shaped vaporizer can be adapted to any specific purpose and/or to the particular units concerned, so that round, cylindrical or angular bell-shapes are possible. In cases of special mountings it can however also be advantageous if the additional vaporizer actually surrounds the units from all sides, that is to say if the base surface is also surrounded by the vaporizer.

The additional vaporizer can be so designed that it additionally extracts a certain proportion of heat from its external environment. In that case, the additional vaporizer is not heat-insulated either internally or externally, Tf however, the additional vaporizer is only intended to take up the residual heat released by the units, it is advisable to provide it, on the outside, with a heat-insulating layer.

However, in certain cases, namely when the additional vaporizer is intended not only to take up the residual heat, but at the same time to cool the space in which it is installed, it can also be advantageous to attach the heat insulation to the inner surface of the additional, beil-shaped vaporizer. Between the units and the internally insulated additional vaporizer there may be a small vaporizer which merely serves to absorb the heat of the inner space and to keep the inner space at a certain temperature. This embodiment is advantageous since in this way the actual "boiler basement" can be converted to a refrigerated room. The foodstuffs and/or beverages introduced into this refrigerated room additionally provide the total system with heat energy, at no cost, thus increase the efficiency of the installation.Depending on the amounts of heat which are to be absorbed from the inner and/or outer surfaces via the additional vaporizers, it can be advantageous to insulate the inner surfaces and/or outer surfaces with different thicknesses of insulating material and/or to insulate them partially only. In this way it can become possible to dispense with the small vaporizer which in the embodiment described above is located between the units and the inner face of the additional vaporizer.

All commercially available insulating materials can be used as the heat insulants.

Because of the very good heat insulating properties, polyurethane foams are preferably used, however, for the heat insulation of the additional vaporizer.

In order above all to utilize to the greatest possible extent the heat of combustion generated by the combustion engine and possibly also the heat released by the compressor a description of surrounding the combustion engine and, where relevant, the gearbox and the compressor with a heatinsulating housing was given at the outset.

Preferably, the units are directly embedded in foam. The wet exhaust gas scrubber described above can also carry such a directly foamed-on heat-insulating housing and can also be located underneath the additional vaporizer. The automatically resulting increase in operating temperature associated with the embedding in foam, for example the increase in operating temperature of the combustion engine and of the compressor, is compensated by a correspondingly greater throughput of cooling medium, in which case a further, controlled removal of the heat of combustion and heat of compression, with transfer of this heat to the heating system, takes place at the same time, so that the additional vaporizer in that case really only has to absorb small residual amounts of heat.

The working medium for the additional vaporizer or vaporizers is preferably branched off the main working medium circuit, which passes through the actual vaporizer, which abstracts the heat from its environment, that is to say the air, ground water or soil. The additional vaporizers can -in respect of the working medium-be connected in parallel or in series.

The temperature in the space which may be present between the inner surfaces of the additional vaporizer and the units is kept at the desired level by means of appropriate temperature regulating and control instruments.

For further explanation of this embodiment of the invention, attention is drawn to the appended Figures 2 and 3.

Figure 2 shows, in schematic representation, an arrangement according to the invention, in which the compressor 2, the drive device 15, the gearbox 1, the heat exchanger 29, the shared additional vaporizer 25, the heat-insulating layer 28 applied to the inside of the additional vaporizer 25, the actual vaporizer 27, the pipelines 30 for the working medium and the refrigerated space 31 are shown.

Figure 3 shows, in perspective view, the U-shaped additional vaporizer 25 having an external heat-insulating layer. On the two open sides, appropriate vaporizer parts are attached, which can be connected in series with the working medium of the U-shaped part.

With heating units according to the invention, the maximum degrees of energy utilization can be achieved if all the intermediate heat exchangers, both on the vaporizer side and on the heating side, are omitted. This leads to working medium vapor heating, in which the vaporizer is also directly exposed to the external atmosphere. In addition, it is necessary to work with the minimum possible temperature spread. These maximum degrees of energy utilization can be achieved with floor heating, in which the heating pipes laid in the floor screed at the same time represent the condenser. The heat exchanger acting as a vaporizer must in that case be designed to have such a large surface area that changes due to formation of ice will not have a harmful influence on the heat resistance.

In heating units of the present invention, the heat pump is driven by a combustion engine, a diesel engine preferably being employed. Of course, however, all other types of combustion engines can also be used for driving the heat pump, provided that the liquid or gaseous fuels to be burned in the combustion engine ensure economical operation of the powered heating unit. The speed of rotation of the combustion engine required in any particular case depends on the external temperature, since at higher external temperatures a small temperature spread in the heat pump, and at low external temperatures a large temperature spread in the heat pump, are required.

In the heating units of the invention regulation of the throughput of heat transfer medium is effected by regulating the speed of revolution of the combustion engine. At constant speed of revolution of a piston compressor or turbo-compressor for example, a lower throughput of working medium would be set up at higher temperatures than at lower temperatures, that is to say precisely contrary to requirements, since at higher temperatures the throughput of working medium should be higher than at low temperatures. This means that at higher external temperatures the drive shaft of the combustion engine must rotate more slowly, whilst at low external temperatures it must rotate more rapidly.For this reason, in heating units of the invention, the throughput of working medium is regulated byl regulating the speed of revolution of the engine as a function of the temperature of the environment of the vaporizer of the heat pump, and as a function of the temperature spread resulting therefrom. Additionally to such regulation, the speed of revolution of the compressor can be regulated by an infinitely variable belt drive (Trade Mark- Variomatic) or the like.

When carrying out the invention in practice, the drive of the heat pump by means of a combustion engine can of course also be coupled to an electric motor, namely in cases where favourable electricity tariffs are available at low load times, which, as is known, are also low heating times. In that case, the coupling is such that the combustion engine only drives the heat pump during the times when intense heating is required, and at all other times the substantially smaller-sized electric motor functions as the drive.

As explained at the outset it is desirable to increase the life of the combustion engines and compressors of the heat pumps employed for powered heating units, and this is achieved by, on the one hand, fitting one or more heat accumulators into the heating system of the powered heating unit and, on the other hand, designing the combustion engine and the compressor of the heat pump to be at least twice as powerful as would be necessary for normal heating of the heating system, including the heat accumulators.

Normal heating in this context is to be understood as the heating capacity which is required pro rata for most of the time, that is to say for at least 70to of the duration of the heating period.

As a result of building the heat accumulator or accumulators into the heating system, the alternating operating times and pause times of the combustion engine of the powered heating unit are relatively long.

This has an advantageous effect on the life of the combustion engine, especially of the diesel engine, since it is known that all combustion engines undergo wear particularly during frequent starting sequences and during cold-running periods.

By making the combustion engine, and the compressor of the heat pump, driven by the combustion engine, substantially over-size, relatively short operating periods, compared to the pauses, are achieved. If, for example, the diesel engine and the compressor are only intended to run for 50% of the normal operating time, they must be of twice the dimensions, as a result of which, in this case, the life of the diesel engines and compressor is doubled. Of course, it is a precondition that even the halved operating times, resulting from the heat accumulator or accumulators, are still relatively long.

As may be seen from the above comments, the use of heat accumulators in itself already results in an increase in the working life of the combustion engines and compressors of normal dimensions for the particular powered heating unit, since the cold-running phases of the combustion engine are relatively short compared to the hot-running phases, and the number of switching-on and switching-off sequences is reduced.

In exactly the same way, the use of overdimensioned combustion engines and compressors alone (without the use of heat accumulators) already achieves a certain increase in the working life of the combustion engines and compressors, though this life is again greatly reduced by the frequent switching-on and switching-off sequences and the increase in the cold-running phases, associated therewith.

Accordingly, the actual increase in the working life of the combustion engine and compressor of the powered heating unit is only achieved by the combination of heat accumulators and over-dimensioning of the combustion engine and compressor. At the same time, this combination results in a further improvement in the degree of energy utilization of the powered heating unit, since, according to experience, every switch- ing-on sequence reduces the degree of energy utilization of the installation.

The heat accumulators, when provided, are thermally well-insulated containers which are filled with the fluid of the particular heating system and are connected to the said system, and have the fluid of the said system flowing through them.

Of course, it is however also possible to use, as the heat accumulators, efficiently heat-insulated containers filled with any desired medium, which are heated by the particular heating system, via heat exchangers.

It is true that these containers are preferably filled with water, but it is equally possible to employ, as the medium, other fluids or even solids which accumulate heat more efficiently and again release it efficiently, for example solids in the form of a powder.

If it is intended that the heating system of the powered heating unit should consist of several separate heating systems, as is the case, for example, according to the embodiment described in connection with Figure 1, a heat accumulator can be allotted to one, several or each particular heating system.

For example, a heat accumulator can be located in the warm water circulation of the heating system which is heated by the heat pump via the heat exchanger, and/or in the warm water circulation of the heating system which is heated by the combustion gases of the combustion engine and of the heating system which is heated byi the heated cooling medium of the combustion engine, via a heat exchanger, and/or in the working medium circulation of the heat pump, in which latter case the working medium of the heat pump serves for direct space heating.

However, preferably the individual heating systems are coupled to form a coherent heating system into which only one heat accumulator is fitted, which is heated via appropriate heat exchangers both by the heat released by the heat pump and by the heated cooling medium of the combustion engine and the hot combustion gases of the combustion engine. Admittedly, it can be ad- vantageous, in the latter case, if the single heat accumulator is replaced by two or more heat accumulators connected in series in order to be able better to utilize the temperature gradient of the individual separate heat exchangers, which are heated by the heat pump, the heated coolant of the combustion engine and the hot combustion gases.

If desired, heat exchangers are additionally located in the heat accumulator in order to produce warm process water from cold tap water by a continuous flow process, if appropriate in conjunction with a warm water storage unit located in the heat accumulator.

In the text which follows, the provision of heat accumulators is explained in relation to Figures 4 to 7. They represent portions, of the embodiment shown in Figure 1.

Figure 4 shows schematically a portion of a powered heating unit in which only one heat accumulator 21 is present in the entire system, namely in the warm water circuit of the partial heating system 8 which is heated by the heat pump via a heat exchanger 4.

Figure 5 shows schematically a portion of a powered heating unit in which only one heat accumulator 22 is present in the entire system, namely in the warm water circuit of the partial heating system 10 heated by the combustion gases of the combustion motor and by the heated cooling medium of the combustion engine 15 via heat exchangers 13 and 3.

Figure 6 shows schematically a portion of a powered heating unit in which only one heat accumulator 23 is present in the entire system, namely in the working medium circuit, with the working medium of the heat pump serving for direct space heating.

As may be seen from this figure, it is necessary, with this arrangement, that the heat accumulator should be located downstream of the space heaters 8.

Figure 7 shows schematically a portion of a powered heating unit in which the individual partial heating systems form a ceherent heating system, in which only one heat accumulator 24 is provided, which is heated (via corresponding heat exchangers, both by the heat released by the heat pump and by the heated cooling medium of the combustion engine and the hot combustion gases of the combustion engine. Furthermore it can be seen from this figure that the heat accumulator 24 is additionally provided with a heat exchanger 25 by means of which cold tap water is heated by a continuous flow process, to give warm process water.

In Figures 4 to 7 the heat accumulators have been drawn separately, as they can also be constructed in the form of a unit with the corresponding heat exchangers.

The list of reference numbers which follow contains the reference numbers given in Figures 1 to 7.

1 Gearbox 2 Compressor 3 Heat exchanger I for cooling water circuit and for wet off-gas heat ex changer 4 Heat exchanger II for heat pump circuit 5 Insulating mat 6 Circulating pump 7 Bottom 8 Heater 9 Circulating pump 10 Heater 11 Vaporizer 12 Chimney 13 Wet off-gas heat exchanger 14 Exhaust of the diesel engine 15 Diesel engine 16 Vibration-damping noise-damping engine bearing 17 Foundations 18 Throttle 19 Non-return safety valve 20 Pump 21 Heat accumulator of the warm water circuit of the heat pump 22 Heat accumulator of the warm water circuit which is heated by the com bustion gases of the combustion engine and by the cooling medium of the combustion engine.

23 Heat accumulator of the working medium circuit of the heat pump 24 Heat accumulator of the warm water circuit, which is heated by the heat pump, the combustion gases of the combustion engine, and the cooling medium of the combustion engine 25 Additional vaporizer 26 External heat-insulating layer 27 Actual vaporizer 28 Internally fitted heat-insulating layer 29 Heat exchanger 30 Pipelines for the working medium 31 Refrigerated space As may be seen from the above, it is possible, with the aid of the powered heating unit according to the invention, to reduce the primary energy consumption greatly and to increase the working life of the combustion engine and of the compressor.A further advantage of the powered heating unit is that the combustion gases which it gives off cause less pollution of the environment than those in the case of a fuel oil burner system, and that it presents less of a fire hazard than the fuel oil burner systems. In the case of oil burners, fires easily result from the fact that the pilot flame of the oil burner system simulates a flame, which causes the formation of an oil mist in the boiler, which mist ignites explosively under certain circumstances.

WHAT WE CLAIM IS: - 1. A powered heating unit comprising a combustion engine, a heat pump comprising a compressor driven by said combustion engine and a vaporizer, a heat transfer medium circulation system coupled to said compressor and vaporizer for providing heat to a heating system and means for feeding waste heat energy of said combustion engine into said heating system or into at least one further heating system, the combustion engine being arranged within a heat insulating housing, means being provided for regulating the throughput of the heat transfer medium in the heat transfer medium circulation system in dependency of the temperature of the environment of the vaporizer of the heat pump by controlling the speed of rotation of said combustion engine.

2. A heating unit as claimed in claim 1, wherein said heat insulating housing extends also around a gearbox provided be

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. Figure 5 shows schematically a portion of a powered heating unit in which only one heat accumulator 22 is present in the entire system, namely in the warm water circuit of the partial heating system 10 heated by the combustion gases of the combustion motor and by the heated cooling medium of the combustion engine 15 via heat exchangers 13 and 3. Figure 6 shows schematically a portion of a powered heating unit in which only one heat accumulator 23 is present in the entire system, namely in the working medium circuit, with the working medium of the heat pump serving for direct space heating. As may be seen from this figure, it is necessary, with this arrangement, that the heat accumulator should be located downstream of the space heaters 8. Figure 7 shows schematically a portion of a powered heating unit in which the individual partial heating systems form a ceherent heating system, in which only one heat accumulator 24 is provided, which is heated (via corresponding heat exchangers, both by the heat released by the heat pump and by the heated cooling medium of the combustion engine and the hot combustion gases of the combustion engine. Furthermore it can be seen from this figure that the heat accumulator 24 is additionally provided with a heat exchanger 25 by means of which cold tap water is heated by a continuous flow process, to give warm process water. In Figures 4 to 7 the heat accumulators have been drawn separately, as they can also be constructed in the form of a unit with the corresponding heat exchangers. The list of reference numbers which follow contains the reference numbers given in Figures 1 to 7.

1 Gearbox

2 Compressor

3 Heat exchanger I for cooling water circuit and for wet off-gas heat ex changer

4 Heat exchanger II for heat pump circuit

5. A powered heating unit, substantially as herein described with reference to and as shown in the accompanying drawings.

5 Insulating mat

6 Circulating pump

7 Bottom

8 Heater

9 Circulating pump

10 Heater

11 Vaporizer

12 Chimney

13 Wet off-gas heat exchanger

14 Exhaust of the diesel engine

15 Diesel engine

16 Vibration-damping noise-damping engine bearing

17 Foundations

18 Throttle

19 Non-return safety valve

20 Pump

21 Heat accumulator of the warm water circuit of the heat pump

22 Heat accumulator of the warm water circuit which is heated by the com bustion gases of the combustion engine and by the cooling medium of the combustion engine.

23 Heat accumulator of the working medium circuit of the heat pump

24 Heat accumulator of the warm water circuit, which is heated by the heat pump, the combustion gases of the combustion engine, and the cooling medium of the combustion engine

25 Additional vaporizer

26 External heat-insulating layer

27 Actual vaporizer

28 Internally fitted heat-insulating layer

29 Heat exchanger

30 Pipelines for the working medium

31 Refrigerated space As may be seen from the above, it is possible, with the aid of the powered heating unit according to the invention, to reduce the primary energy consumption greatly and to increase the working life of the combustion engine and of the compressor.A further advantage of the powered heating unit is that the combustion gases which it gives off cause less pollution of the environment than those in the case of a fuel oil burner system, and that it presents less of a fire hazard than the fuel oil burner systems. In the case of oil burners, fires easily result from the fact that the pilot flame of the oil burner system simulates a flame, which causes the formation of an oil mist in the boiler, which mist ignites explosively under certain circumstances.

tween the engine and the compressor, as well as around the compressor, heat sensitive subsidiary units of the engine being arranged outside said housing.

3. A heating unit as claimed in claim 1 or 2, wherein the housing is foamed directly on to the combustion engine, parts of the housing being removable at those points of the engine which require access for servicing.

4. A heating unit as claimed in claim 1, 2 or 3, wherein the heat insulating housing consists of polyurethane foam.