EP2122039B1 - Condensation dryer having a heat pump and method for the operation thereof - Google Patents

Abstract

A condensing dryer comprises a chamber (3) for drying objects, a fan-driven (19) processing air circuit (2) and a heat pump circuit (13,14,15,23) to alternately warm and cool the processing air. There is a secondary fluid circuit (12,20,16,21) between the processing air and heat pump circuits. Preferably the secondary fluid is a liquid at normal temperature and pressure and comprises water or an alcohol and glycol ether.

Description

The invention relates to a condensation dryer with a drying chamber for objects to be dried, a process air circuit in which the process air can be guided by means of a blower over the objects to be dried, and a heat pump circuit for alternately heating and cooling the process air.

The invention also relates to a method of operating such a condensation dryer.

Tumble dryers, whose operation is based on the condensation of moisture vaporized by means of warm process air from the laundry - so-called condensation dryers - are very popular because they produce no exhaust air laden with moisture and no hose for dissipating this exhaust air from a building in which such a tumble dryer is set up. Condensation dryers can therefore be used in internal bathrooms or laundry rooms of larger residential complexes.

In a condensation dryer process air is passed through a fan via a heater in the wet laundry containing drum as a drying chamber. The hot air absorbs moisture from the laundry to be dried. After passing through the drum, the now moist process air is directed into a heat exchanger, which is usually preceded by a lint filter.

In the heat exchanger (eg air-air heat exchanger), the moist process air is cooled, so that the water contained in the moist process air condenses. The condensed water is then collected in a suitable container. The cooled and dried air is then returned to the heater and then to the drum. In general, the heat exchanger can be easily removed for occasional cleaning of dried lint (microfibers of the laundry).

This drying process is very energy-intensive, since the heat extracted for cooling the process air in the heat exchanger is energetically lost to the process. By using a heat pump, which in some cases supplies this extracted heat to the process air, it is generally possible to save about 50% of the energy used. In a known condensation dryer equipped with a heat pump, the cooling of the warm, moisture-laden process air takes place in an evaporator of the heat pump. A refrigerant of the heat pump evaporating by taking heat from the process air is compressed in a compressor and supplied to a condenser where it releases heat by condensation, which in turn is used to heat the process air before entering the laundry drum. Behind the condenser, the refrigerant flows through a throttle, where its pressure is reduced to a lower value, so that it can evaporate in the evaporator, in which it then returns, with renewed absorption of heat.

In the DE 40 23 000 C2 a tumble dryer with a heat pump is described, in which a supply air opening is arranged in the process air channel between the condenser and the evaporator, which is closable with a controllable closure device.

In the DE 197 38 735 C2 a condensation dryer with a closed process air circuit is described, which is equipped with a heat pump. The heat pump is designed as a device operating according to the absorber principle whose absorber forms a third heat exchanger whose coolant flows through the primary circuit and via whose secondary circuit the process air flowing from the second heat exchanger is returned to the secondary circuit of the first heat exchanger.

In the condensation dryers known hitherto, the heat exchange between the heat pump and the process air takes place directly.

The problem with the use of a heat pump, the pollution of the two heat exchangers in the heat pump (evaporator, condenser), especially the evaporator by entrained lint. Unfortunately, the fluff contained in the process air can not be completely separated in the lint filter, since an improvement in the filter performance of the lint filter is accompanied by an increase in its flow resistance. The fluff deposited as a film, for example, on the cooling fins of the heat exchanger and thus increase the heat transfer resistance, whereby the efficiency of the heat exchanger is reduced.

Since evaporator and condenser of a heat pump are generally fixed and connected to the compressor by pressure-tight piping, they can not be removed for cleaning.

Another problem is in the piping between heat exchangers and compressor. Modern heat pumps often use carbon dioxide as a refrigerant. This very environmentally friendly refrigerant works only at extremely high pressure (up to 145 bar). There are therefore very high demands on the tightness of the refrigerant circuit. In addition, the heat exchangers can not be optimally placed in the process air flow, otherwise the refrigerant lines would be too long. In addition, the industrial production of the system compressor, evaporator, condenser with the high pressure lines connecting them is very difficult to realize cost-effective. Similar problems occur with other refrigerants used in heat pumps.

These disadvantages of the known condensation dryer with heat pumps lead to a reduction in the life and due to the poor cleaning capabilities of the heat exchanger to a deteriorated energy balance.

An object of the invention is therefore to provide a condensation dryer with a heat pump, which has an increased life and offers the possibility for easier cleaning.

The solution of this object is achieved according to this invention by a condensation dryer with the features of claim 1 and the method of claim 9.

Preferred embodiments of the condensation dryer according to the invention are listed in the subclaims 2 to 8. A preferred embodiment of the method according to the invention is listed in claim 10.

The invention thus relates to a condensation dryer with a drying chamber for objects to be dried, a process air circuit in which the process air can be guided by means of a blower on the objects to be dried, and a heat pump circuit for alternately heating and cooling the process air, in which condensation dryer between at least one secondary fluid circuit is located in the process air circuit and the heat pump circuit.

The invention also provides a method for operating a condensation dryer with a drying chamber for objects to be dried, a process air circuit in which the process air is guided by means of a blower over the objects to be dried and thereby alternately heated and cooled by a heat pump cycle, wherein between the process air circuit and the heat pump circuit is at least one secondary fluid circuit through which heat is exchanged between the heat pump circuit and the process air.

In a preferred embodiment of the condensation dryer according to the invention, the secondary fluid circuit contains a secondary refrigerant which is a substance which is liquid at room temperature and normal pressure. Preferably, in this case, the secondary refrigerant in a secondary fluid circuit at least one substance from the group consisting of water, single and multiple alcohols and glycol ethers. Suitable polyhydric alcohols are, for example, ethylene glycol and propylene glycol. Suitable glycol ethers are, for example, ethylene glycol dimethyl ether and propylene glycol dimethyl ether or the corresponding monoether. Most preferably, water is used as the secondary refrigerant.

In addition, it is preferable to use a primary refrigerant in the heat pump cycle selected from the group consisting of propane, isobutane, carbon dioxide and fluorohydrocarbon compounds. In this case, furthermore, the heat pump preferably has an evaporator, a condenser, a compressor and a throttle. The compressor is generally in the flow direction of the primary refrigerant between the evaporator and the condenser. In general, in addition, in the heat pump in the flow direction of the primary refrigerant between the condenser and the evaporator, an expansion valve, also referred to as throttle. The primary refrigerant used in the heat pump preferably circulates in the heat pump cycle with a turbulent flow. Turbulent flow may be adjusted by suitable design of a flow channel and / or by suitable drive means (e.g., compressor).

The condensation dryer according to the invention contains at least one secondary fluid circuit between the heat pump and the process air circuit. In other words, there is at least one first or second secondary fluid circuit between the process air circuit and the heat-absorbing heat exchanger (in particular evaporator) of the heat pump or between the process air circuit and the heat-emitting heat exchanger (in particular condenser) of the heat pump. Preferably, one or two secondary fluid circuits are located between the heat pump and the process air circuit. Most preferably, the condensation dryer according to the invention has a first secondary fluid circuit and a second secondary fluid circuit.

In each secondary fluid circuit, a secondary refrigerant, which is generally different from the primary refrigerant, circulates.

In the condensation dryer according to the invention, the heat pump thus gives its cooling power or heating power via a secondary refrigerant (also called "secondary fluid") in at least one secondary fluid circuit to the process air circuit of the Condensation dryer off. Thus, the cooling or heating power is generated centrally in a heat pump, which can be very compact in the condensation dryer according to the invention.

If, in one embodiment of the invention, there is a secondary fluid circuit between the process air circuit and the evaporator of the heat pump, the warm, moisture-laden process air is cooled in a first heat exchanger in which the process air circuit and the first secondary fluid circuit contact via a good heat-conducting wall , The moisture contained in the process air condenses and is generally collected in a suitable receptacle, e.g. a bowl, collected from where it is disposed of.

If, in one embodiment of the invention, there is a secondary fluid circuit between the process air circuit and the heat-emitting heat exchanger of the heat pump, the dried, cooled process air is heated in a second heat exchanger in which the process air circuit and the second secondary fluid circuit contact via a wall which is as heat-conductive as possible , The heated process air is then in turn supplied to the laundry drum as a drying chamber. Before the second heat exchanger or preferably between the second heat exchanger and the laundry drum, the process air can be additionally heated by an electric heater.

The secondary refrigerant ("secondary fluid") is most preferably water. Since this can be done almost pressure-free relative to the ambient pressure, the flowed through by the process air heat exchanger between the heat pump and the process air circuit, for example via quick-release closures (as used similarly as articles for garden irrigation) are connected to the heat pump.

The secondary refrigerant used in the secondary fluid circuit, preferably water, is generally supplied via an external inlet (water inlet).

In a preferred embodiment in which water is used as the secondary refrigerant, the condensation water obtained during the drying process is at least partly used as a secondary refrigerant.

The temperature of the secondary refrigerant and the temperature of the primary refrigerant are generally kept within the allowable range by the control of the heat pump. If, in the condensation dryer according to the invention in the process air circuit before the entry into the drying chamber is preferably a heating, generally takes place the control of the heat pump in coordination with the control of the heater.

It is preferred if the condensation dryer according to the invention has a first secondary fluid circuit and a second secondary fluid circuit, so that both heat exchangers of the heat pump are each connected to the process air circuit via a secondary fluid circuit.

It is particularly advantageous if the condensation dryer according to the invention has at least one removable heat exchanger. The removable heat exchanger may be the first and / or the second heat exchanger. According to the invention, the first heat exchanger is preferably removable, since it tends more to contamination with lint.

In a preferred embodiment of the method according to the invention, two secondary fluid circuits are located between the process air circuit and the heat pump circuit, and heat is exchanged between these between the heat pump circuit and the process air.

The heat exchange between the heat pump circuit and the first and second secondary fluid circuit is particularly efficient when the refrigerant is moving in turbulent flow. Preferably, the primary refrigerant in the heat pump circuit is turbulent. However, by suitable design measures (guidance of the refrigerant in a circle) or by suitable process-related measures (suitable conveying means), a turbulent flow can also be set in the secondary fluid circuit and / or in the process air circuit instead of a laminar one. In general, the secondary fluid lines are thermally insulated except for the line sections located in the respective heat exchanger.

According to the invention, it is preferred if process air and primary or secondary refrigerant are passed through the heat exchangers in a cross-flow or countercurrent process.

As the degree of drying of the objects to be dried in the condenser dryer decreases the energy required for drying, it is appropriate to regulate the heating accordingly, that is. As the degree of dryness progresses, their heating power is reduced to maintain a balance between the supplied and necessary drying energy. With increasing degree of drying of the objects to be dried, in particular laundry, thus a lower heating power or even an increasing cooling capacity of the heat pump is required. In particular, after a completed drying phase, the temperature in the process air circuit would rise sharply. In general, therefore, the heat pump and the heater in the condensation dryer are controlled so that a maximum allowable temperature is not exceeded in the drying chamber.

The invention has numerous advantages. The long-term stability of condensation laundry dryers with a heat pump is improved due to the use of secondary fluid circuits. A coefficient of performance of the heat pump cycle increases, with a slight reduction in the coefficient of performance due to the at least one secondary circuit (increase in the number of heat transfers) being more than offset by the elimination of the problems with contaminated heat exchangers.

In the embodiment of the condensation dryer according to the invention, in which an easily detachable connection of the secondary fluid supply or discharge is provided, the heat exchanger through which the process air flows can be very easily disassembled and cleaned. As a result, the performance of the heat exchanger is maintained.

In the condensation dryer according to the invention, the heat pump unit can be very compact, in particular from compressor, evaporator, throttle and condenser prefabricated. After installation, only the secondary fluid lines need to be connected. This makes it much easier and automated to produce the heat pump unit. This reduces the cost of the manufacturing process and enables a higher, easier-to-control manufacturing quality.

The placement of the heat exchangers for the process air is when using very low boiling refrigerants such. Carbon dioxide is no longer bound to narrow limits by the high-pressure lines of the refrigerant circuit.

In embodiments, the secondary fluid may also dissipate the waste heat of the compressor of the heat pump to the process air of the clothes dryer. This increases the overall efficiency of the heat pump process and thus the energy balance of the entire drying process.

A non-limiting exemplary embodiment of a condensation dryer according to the present invention, in which the method according to the invention can also be carried out, is disclosed in US Pat FIG. 1 shown.

When condensation dryer of FIG. 1 the heat pump is connected to the process air circuit via two secondary fluid circuits.

FIG. 1 shows a vertically cut condensation dryer 1 (hereinafter abbreviated to "dryer" 1). The in FIG. 1 shown dryer 1 has a drum 3 rotatable about a horizontal axis as a drying chamber 3, are mounted within which driver 4 for moving laundry during a drum rotation. A heater 18, a first heat exchanger 11, 12, 13, a heat pump 13, 14, 15, 23, a second heat exchanger 16, 17 and a fan 19 are provided to a closed by an air duct 2 process air circuit 2 through the drum 3 through produce, after passing through the drum 3 to cool and reheat after condensation of moisture contained in the process air. It is heated by the heating 18 of behind, ie from the dryer door 5 opposite side of the drum 3, passed through the perforated bottom in the drum 3, comes there with the laundry to be dried in contact and flows through the filling opening of the drum 3 to a lint filter 6 within a filling opening occlusive Drying door 5. Subsequently, the air flow is deflected in the dryer door 5 down and passed from the air duct 2 to the heat exchanger 11, 12. There condenses due to cooling the moisture absorbed by the air from the laundry and is in a in FIG. 1 Not shown condensate container collected, from which it can be disposed of. The heater 18 is optional; Above all, it is provided in order to be able to bring the components of the condensation dryer 1 and the objects to be dried as quickly as possible to the elevated temperatures required for drying during commissioning. In stationary operation of the condensation dryer 1, the use of the heater 18 may no longer be required.

The transmission of the cooling power of the heat pump 13, 14, 15, 23 in this case takes place via the circulating in a first secondary fluid circuit 12, 20 secondary refrigerant, preferably water. After the heat exchanger 11, 12, the process air is passed from the blower 19 in turn to the heater 18. Between the fan 19 and the heater 18 is a second heat exchanger 16, 17, the heat pump 13, 14, 15, 23, in which the process air is heated by means of the heat generated by this. The heat is transferred via a second secondary fluid circuit 16, 21.

The drum 3 is in the in Fig. 1 shown embodiment at the rear bottom by means of a pivot bearing and front mounted by means of a bearing plate 7, wherein the drum 3 rests with a brim on a sliding strip 8 on the bearing plate 7 and is held at the front end.

The control of the condensation dryer via a control device 10, which can be controlled by the user via an operating unit 9; the controller engages in a suitable, not to be described in detail manner on all controllable components, including in particular not shown here, conventional sensors, the dryer 1 to.

The heated secondary refrigerant of the first secondary fluid circuit 12, 20 is cooled in the evaporator 13 of the heat pump 13, 14, 15, 23. In the heat pump 13, 14, 15, 23, a primary refrigerant is evaporated in the evaporator 13, compressed in the compressor 14 and then condensed in the condenser 15 of the heat pump. The heat released in this process is used to heat the process air passed through the second heat exchanger 16, 17 via a second secondary circuit 16, 21. From the condenser 15, the refrigerant passes through a throttle 23 back to the evaporator 14. To increase the energy yield, the waste heat of the heat pump circuit 13, 14, 15, in particular of the compressor 14, which is generally operated electrically, the process air are supplied (in FIG. 1 dashed lines drawn).

Claims (10)

1. Condenser dryer (1) with a drying chamber (3) for articles to be dried, a process air circuit (2) in which process air can be guided by means of a fan (19) over the articles to be dried and a heat pump circuit (13, 14, 15, 23) for alternating heating and cooling of the process air, characterised in that at least one secondary fluid circuit (12, 20 or 16, 21) by way of which heat can be exchanged between the heat pump circuit (13, 14, 15, 23) and the process air is disposed between the process air circuit (2) and the heat pump circuit (13, 14, 15, 23).
2. Condenser dryer (1) according to claim 1, in which the secondary fluid circuit (12, 20 or 16, 21) contains a secondary refrigerant which is liquid at room temperature and normal pressure.
3. Condenser dryer (1) according to claim 2, in which the secondary refrigerant in a secondary fluid circuit (12, 20 or 16, 21) is at least one substance from the group consisting of water, simple and multiple alcohols and glycolethers.
4. Condenser dryer (1) according to claim 3, in which the secondary refrigerant is water.
5. Condenser dryer (1) according to any one of claims 1 to 4, in which the heat pump circuit (13, 14, 15, 23) contains a primary refrigerant which is selected from the group consisting of propane, isobutane, carbon dioxide and fluorocarbon/hydrocarbon compounds.
6. Condenser dryer (1) according to claim 5, in which the heat pump circuit (13, 14, 15, 23) comprises an evaporator (13), a compressor (14), a condenser (15) and a throttle (23).
7. Condenser dryer (1) according to any one of claims 1 to 6, which has a first secondary fluid circuit (12, 20) and a second secondary fluid circuit (16, 21).
8. Condenser dryer according to any one of claims 1 to 7, comprising at least one removable first heat exchanger (16, 17) or second heat exchanger (11, 12).
9. Method of operating a condenser dryer (1) with a drying chamber (3) for articles to be dried, a process air circuit (2) in which the process air is guided by means of a fan (19) over the articles to be dried and in that case is alternately heated and cooled by a heat pump circuit (13, 14, 15, 23), characterised in that disposed between the process air circuit (2) and the heat pump circuit (13, 14, 15, 23) is at least one secondary fluid circuit (12, 20 or 16, 21) by way of which heat is exchanged between the heat pump circuit (13, 14, 15, 23) and the process air.
10. Method according to claim 9, in which disposed between the process air circuit (2) and the heat pump circuit (13, 14, 15, 23) are two secondary fluid circuits (12, 20 or 16, 21) by way of which heat is exchanged between the heat pump circuit (13, 14, 15, 23) and the process air.

Images