EP2330360A2 - Thermodynamic water heater with control of water heating - Google Patents

Abstract

The water-heater (10) has an electronic control unit for controlling heating of water based on time. A thermodynamic heat exchanging circuit exchanges heat between flow of air and water to be heated, and is provided with an evaporator (16). A circulation unit i.e. compressor (18), of the thermodynamic heat exchanging circuit circulates refrigerant fluid in a thermodynamic circuit. A condenser (20) transfers heat from the refrigerant fluid to the water to be heated. A cylindrical reservoir (12) receives the water to be heated, and has capacity ranging between 250 and 300 liters.

Description

The present invention relates to a thermodynamic water heater with water heating control.

A thermodynamic water heater is a water heater adapted to at least partially heat the water it contains with the aid of calories included in a flow of air. Conventionally, the airflow is a flow of air in an unheated space - such as a laundry room, a garage or a crawl space - in the outside air or a stream of air extracted from the apartment. This airflow can also be created by means of a fan.

Thermodynamic water heaters are especially used for heating domestic hot water at a temperature between 40 and 65 ° C, for example of the order of 55 ° C.

A thermodynamic water heater mainly comprises a reservoir for containing water to be heated and a thermodynamic circuit for recovering calories from a stream of air in order to heat the water in the tank.

To do this, the air flow passes through an evaporator of the thermodynamic circuit. By passing through this evaporator, the air flow loses calories in favor of a refrigerant, or heat transfer fluid circulating in the thermodynamic circuit.

The refrigerant is set in motion in the thermodynamic circuit.

The refrigerant thus reaches a condenser where the refrigerant yields calories to the water contained in the reservoir. At the same time, the refrigerant condenses.

The refrigerant then arrives, again, at the evaporator.

A thermodynamic water heater further comprises, conventionally, a temperature sensor adapted to measure the temperature of the water in the water heater. An electronic control unit receives the information of the temperature measured by the probe and controls, therefore, a heating of the water if the temperature is below a predetermined threshold.

The control of the water heating may for example consist of controlling the circulation of the refrigerant in the thermodynamic heat exchange circuit.

These devices thus have excellent performance. However, the use of these thermodynamic water heaters remains expensive.

The object of the present invention is to provide a thermodynamic water heater not having this disadvantage.

More particularly, the invention aims to provide a thermodynamic water heater having a lower cost of use than known thermodynamic water heaters.

To this end, the present invention provides a thermodynamic water heater comprising an electronic control unit adapted to control the heating of water depending on the time.

• le chauffe-eau thermodynamique comprend un circuit thermodynamique d'échange thermique entre un flux d'air et l'eau à chauffer, le circuit comprenant :
  • un évaporateur adapté à être traversé par le flux d'air ;
  • des moyens de mise en circulation du fluide frigorigène dans le circuit thermodynamique ;
  • un condenseur pour transférer des calories du fluide frigorigène à l'eau à chauffer ;
• les moyens de mise en circulation du fluide frigorigène sont un compresseur, de préférence à piston rotatif ;
• le compresseur est adapté à fournir une puissance comprise entre 1400 et 3500 W au liquide frigorigène ;
• le circuit thermodynamique comporte en outre un détendeur ;
• le chauffe-eau thermodynamique comprend un réservoir adapté à recevoir l'eau à chauffer, le réservoir présentant de préférence une contenance comprise entre 250 et 300 litres ;
• le condenseur est réalisé sous la forme d'au moins un tube enroulé autour du réservoir ;
• le condenseur est réalisé sous la forme d'au moins deux tubes enroulés autour du réservoir ;
• le au moins un tube présente une section transversale sensiblement semi-circulaire, le côté plan de la section transversale étant en contact avec réservoir ;
• le au moins un tube présente une section transversale de passage du fluide comprise entre 25 à 38 mm² ; et
• le condenseur est réalisé sous la forme de deux plaques co-laminées pour former au moins un conduit, de préférence au moins deux conduits, en contact avec le réservoir.

According to preferred embodiments, the invention comprises one or more of the following features, taken alone or in combination:

• the thermodynamic water heater comprises a thermodynamic heat exchange circuit between an air flow and the water to be heated, the circuit comprising:
  • an evaporator adapted to be traversed by the air flow;
  • means for circulating the refrigerant in the thermodynamic circuit;
  • a condenser for transferring calories from the refrigerant to the water to be heated;
• the means for circulating the refrigerant are a compressor, preferably a rotary piston;
• the compressor is adapted to supply a power of between 1400 and 3500 W to the refrigerant;
• the thermodynamic circuit further comprises an expander;
• the thermodynamic water heater comprises a reservoir adapted to receive the water to be heated, the reservoir preferably having a capacity of between 250 and 300 liters;
• the condenser is in the form of at least one tube wound around the tank;
• the condenser is formed in the form of at least two tubes wound around the tank;
• the at least one tube has a substantially semicircular cross section, the planar side of the cross section being in contact with the reservoir;
• the at least one tube has a cross sectional fluid passage of between 25 to 38 mm ² ; and
• the condenser is made in the form of two co-laminated plates to form at least one duct, preferably at least two ducts, in contact with the reservoir.

• Les figures 1 et 2 représentent chacune un schéma d'un exemple de chauffe-eau thermodynamique.
• La figure 3 représente un graphique de comparaison de la perte de charge dans différents types de condenseurs en fonction de la puissance fournie par le compresseur au fluide frigorigène.

Other characteristics and advantages of the invention will appear on reading the following description of a preferred embodiment of the invention, given by way of example and with reference to the appended drawing.

• The Figures 1 and 2 each represent a diagram of an example of a thermodynamic water heater.
• The figure 3 represents a graph comparing the pressure drop in different types of condensers according to the power supplied by the compressor to the refrigerant.

As shown on the Figures 1 and 2 , a thermodynamic water heater 10 mainly comprises a reservoir 12 - or tank - adapted to contain water to be heated and a thermodynamic circuit 14 of heat exchange between a stream of air and the water to be heated.

In this case, the reservoir 12 is of substantially cylindrical shape to reduce the footprint of the tank. The reservoir 12 has, in this case a volume between 250 and 300 liters. The reservoir has in particular a lateral surface of between 1.25 and 2.1 m ² and a height of between 0.8 and 1.5 m.

• un évaporateur 16, traversé par un flux d'air, dans lequel le flux d'air perd des calories au profit d'un fluide frigorigène, ou fluide caloporteur, circulant dans le circuit thermodynamique ;
• un compresseur 18 pour mettre en circulation le fluide frigorigène dans le circuit thermodynamique, le compresseur permettant également d'augmenter la pression et la température du fluide frigorigène ;
• un condenseur 20, dans lequel le fluide frigorigène perd des calories au profit de l'eau dans le réservoir 12 ;
• un détendeur 22 où la pression du fluide frigorigène est réduite.

The thermodynamic circuit 14 comprises:

• an evaporator 16, traversed by an air flow, wherein the air flow loses calories in favor of a refrigerant or heat transfer fluid circulating in the thermodynamic circuit;
• a compressor 18 for circulating the refrigerant in the thermodynamic circuit, the compressor also for increasing the pressure and temperature of the refrigerant;
• a condenser 20, in which the refrigerant loses calories in favor of the water in the tank 12;
• a pressure reducer 22 where the pressure of the refrigerant is reduced.

To ensure the flow rate of the air flow through the evaporator, it is provided in the example shown on the Figures 1 and 2 a fan 24.

The refrigerant may for example be R134a.

This thermodynamic water heater further comprises an electronic control unit, not visible in the figures, adapted to control the heating of water depending on the time.

Thus, it is possible to program this electronic control unit so that it controls the heating of the water in the water heater preferentially at times when the electric current is the cheapest, that is to say during the "Off-peak hours". This allows a substantial reduction in the cost use of the water heater compared to known thermodynamic water heaters where the heating of water is controlled only according to the need.

Of course, in a complementary manner, the electronic control unit can be adapted to control the heating of the water as needed. However, since the water has been preheated during the period when the electric current is cheaper, this heater will be an additional heater. This heating will be less expensive than in the case where the water would not have been heated during "off-peak hours". This auxiliary heating may be, for example, carried out using an electric heating means.

However, the "off-peak" period is limited in time. In France, for example, it lasts eight hours. Therefore, it is advantageous that the heating of the water in the tank can be achieved in this lapse of time.

To ensure rapid heating of water in the tank, the compressor 18 can be adapted to provide a power of between 1400 and 3000 W to the refrigerant. To do this, the compressor may for example have a displacement of more than 11 cm ³ .

In addition, the compressor 18 is, in this case, a rotary compressor This type of compressor is indeed more efficient than a conventional piston compressor, that is to say a compressor where the piston is moved in translation. By more powerful means that a rotary compressor has better mechanical, electrical and isentropic efficiencies. In particular, the rotary compressor has an isentropic efficiency of the order of 25% greater than the isentropic efficiency of a piston compressor.

To enable a large amount of the power supplied by the compressor 18 to be supplied to the water to be heated, the condenser has a contact surface with the reservoir 12 of between 0.5 and 1 m ² . Preferably, in order to further increase the efficiency of the heat transfer between the refrigerant and the water to be heated, a thermal paste is placed between the condenser and the reservoir.

In addition, the condenser can be made in the form of a sandwich. More specifically, in this case, the condenser comprises two plates, for example aluminum. The two plates each have a screen-printed side so that once co-cold-rolled, the two plates form a conduit. After rolling, the duct is expanded by pressurizing dry air to increase the contact surface of the refrigerant circuit with the reservoir.

This condenser can also be made in the form of a tube wound around the tank. To maintain a contact surface of the condenser with the reservoir in the range mentioned above, the tube may have a semicircular section whose plane side is in contact with the reservoir.

However, the power provided by the compressor 18 allows both to heat the refrigerant and increase its pressure. The pressure of the refrigerant can thus typically reach about twenty bars. Therefore, it has been found an increase in pressure losses in the thermodynamic circuit, especially in the condenser, due to the power transmitted by the compressor to the refrigerant.

To reduce the pressure losses in the condenser, the tube or the conduit of the condenser preferably has a transverse section for the passage of the fluid of between 50 and 75 mm ² .

However, it has been found that the tube or conduit, conventionally made of aluminum, copper or stainless steel, of such a size presents risks of deformation due to the high pressure of the refrigerant in the condenser.

To prevent the condenser from deforming and further reducing the losses, it is proposed to make the condenser in the form of at least two tubes 20a, 20b wound in parallel around the tank 12. The two tubes 20a, 20b have a cross section of the refrigerant between 25 and 38 mm ² .

Alternatively, it is proposed to make the sandwich type condenser so that it has at least two parallel ducts, the refrigerant passage section is between 25 and 38 mm ² .

The figure 3 illustrates the head losses in the condensers mentioned above as a function of the power supplied to the refrigerant. The curves 30, 32, 34 respectively correspond to a single-duct sandwich-type condenser, to a single-tube condenser and to a two-parallel-tube condenser, these three condensers being of the type adapted to an application in the field of thermodynamic water heaters. In particular, the three condensers studied have comparable exchange surfaces with the water tank.

This graph clearly shows that the use of a two-tube condenser maintains the pressure losses at a level well below the level of the losses in a condenser according to one of the two other types of condenser. A gain of at least one bar is thus obtained at 1500W. This gain rises to more than 3.5 bars at the power of 3500 W. The reduction of the pressure drops in the condenser makes it possible to transmit a greater power to the water to be heated. This allows to heat the water faster.

Of course, the present invention is not limited to the examples and to the embodiment described and shown, but it is capable of numerous variants accessible to those skilled in the art.

Claims (10)

Thermodynamic water heater (10) comprising an electronic control unit adapted to control the heating of the water according to the time. The thermodynamic water heater according to claim 1, further comprising a thermodynamic heat exchange circuit between a stream of air and the water to be heated, the circuit comprising: an evaporator (16) adapted to be traversed by the air flow; - Means (18) for circulating the refrigerant in the thermodynamic circuit; a condenser (20) for transferring calories from the refrigerant to the water to be heated. Thermodynamic water heater according to claim 2, wherein the means for circulating the refrigerant comprises a compressor, preferably a rotary piston. A thermodynamic water heater according to claim 3, wherein the compressor is adapted to provide a power of between 1400 and 3500 W to the refrigerant. Thermodynamic water heater according to any one of the preceding claims, comprising a reservoir adapted to receive the water to be heated, the reservoir preferably having a capacity of between 250 and 300 liters. Thermodynamic water heater according to claims 2 and 5 in combination, wherein the condenser (20) is in the form of at least one tube wound around the reservoir (12), preferably two tubes. Thermodynamic water heater according to claim 6, wherein the condenser (20) is formed as at least two tubes wound around the tank (12). A thermodynamic water heater according to claim 6 or 7, wherein the at least one tube has a substantially semicircular cross section, the planar side of the cross section being in contact with the reservoir (12). Thermodynamic water heater according to one of claims 6 to 8, wherein the at least one tube has a cross sectional fluid passage of between 25 to 38 mm ² . Thermodynamic water heater according to claims 2 and 5 in combination, wherein the condenser is in the form of two co-laminated plates to form at least one duct, preferably at least two ducts, in contact with the reservoir (12) .

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