EP4116482A1

EP4116482A1 - A heat pump dryer comprising a heater group

Info

Publication number: EP4116482A1
Application number: EP22183683.6A
Authority: EP
Inventors: Erdinc DURAK; Mehmet Inan; Selcuk KARAGOZ; Onur ERCAN; Cem YONAR
Original assignee: Arcelik AS
Current assignee: Arcelik AS
Priority date: 2021-07-08
Filing date: 2022-07-07
Publication date: 2023-01-11

Abstract

The present invention relates to a heat pump dryer (1) comprising a body (2); a drum (3) which is provided in the body (2) and wherein the laundry is loaded; a fan (4) which is provided in the body (2) and which provides the air flow into the drum (3); a heat pump (5) which is positioned next to the fan (4); and a heater group (9) disposed on the drum (3) wall and having at least one heater wire (6) over which the process air leaving the fan (4) passes, a heater support member (7) and a safety member (8).

Description

The present invention relates to a heat pump dryer comprising a heater group with improved safety.
Today, it is aimed to provide energy efficiency and time saving with the heat pump dryers that enable the users to use their time in the most efficient way. In dryers that perform drying only with heat pumps, the cycle is completed in relatively long periods and the needs of the users cannot be met. With the hybrid type dryers that use both a heater and a heat pump, it becomes possible to prevent this problem and especially to increase savings in time. By means of the additional heater integrated into the heat pump system, low drying times can be achieved. Typically, the user can activate the hybrid function with a button provided on the control panel. Thus, an algorithm which simultaneously operates the heater and heat pump is run by the control unit.
R134a is generally used as a refrigerant in hybrid dryers. However, instead of this gas, which has a very high GWP (global warming potential), it is encouraged to use more environmentally-friendly gases, which is important in terms of sustainability. On the other hand, the biggest obstacle with gases having low GWP values is the high flammability value of the gases, which requires the need for taking precautions related to combustion reliability. R290 gas is a gas with low GWP and high flammability. The experimental and regulatory flashover temperature of R290 gas is accepted as 350°C. The wire surface temperatures of the open wire electric heater used in the state of the art reach 700°C and cause a great risk in terms of product safety. In the most extreme operating conditions of the products, it is necessary to carry out the design process by taking these limits into account. Therefore, the need for a heater design that can operate at operating temperatures below the flashover temperature (350°C) of R290 gas arises. Furthermore, these limits also apply to safety members such as thermal fuses and thermostats that are operated together with the heater. As a general working principle, the air passes over the heater by means of a fan and is sent into the drum to dry the laundry. Since the temperatures of the heater wires are very high, the air is heated too much, and the temperature exceeds the drum inlet air temperature, which is an experimentally measured 120°C, so as to pose a safety risk. Two safety members are provided on the outer metal sheet of the heater in order to prevent security risks. Such members, which are used as thermal fuses and thermostats, open contacts mechanically when a critical temperature is reached. The air passing over the state of the art safety members by forced convection and radiation is heated by the high temperature of the heater wires.
The operating condition that creates the riskiest product reliability problem is the absence of drum and fan movement. If there is no air flow over the heater when the drum is full of laundry and the fan and drum are not working, the temperatures on the heater surface rise very quickly. The temperature of open wire heaters rises up to 700-800°C and heats the area where the safety members are positioned quickly by radiation, thus keeping the system safe. In products where R290 gas is used, the heater surface must not exceed 350°C under any circumstances, and this cannot be achieved with the existing safety member positions. Therefore, a new heater and safety member design is needed for refrigerants with a relatively low flashover temperature such as R290 gas, and the state of the art does not offer a solution to this technical problem.
In the state of the art International Patent Document No. WO2011151213A2 , a dryer is disclosed, wherein an additional heater is disposed between the condenser and the drum and the drying air is passed over said heater to be sent into the drum, thus providing energy efficiency.
In the state of the art International Patent Document No. WO2020100085 , a hybrid dryer is disclosed, wherein a heater group having a pipe-type heater in the form of fins is used for heating both air and water; however, no solution is provided for using safety members to determine the surface temperature.
The aim of the present invention is the realization of a dryer with improved safety of usage and product performance in dryers wherein environmentally-friendly refrigerant gases are used.
The heat pump dryer realized in order to attain the aim of the present invention, explicated in the claims, comprises a body; a drum which is provided in the body and wherein the laundry is loaded; a fan which is provided in the body and which provides the air flow into the drum; a heat pump which is positioned next to the fan; and a heater group disposed on the drum wall and having at least one heater wire over which the process air leaving the fan passes, a heater support member and a heater safety member. Typically, an air flow path is followed, wherein the process air leaving the fan passes over the heater group to reach the drum, which is mostly used as open wire, and is sent back to the fan after the condensation and evaporation processes in the heat pump. The heater safety member generally operates like a heat sensor and serves as a mechanical switch according to the surface / ambient temperature. The dryer comprises the heater group further having a heater body which is designed as a metal tube and wherein the heater wires therein are surrounded by resistance powder, at least one heater fin which is disposed at the side of the heater body and provides the heat transfer and the air passage, and a heater fin gap on the heater fin wherein at least one safety member is disposed. Thus, in the dryers wherein highly flammable environmentally-friendly refrigerants are used, product and user safety is provided by means of the safety members which keep the temperature of the heater body, of the heater fin and of the surface under a certain threshold.
In an embodiment of the present invention, the heat pump dryer comprises the safety member which is a fuse and / or thermistor fixed by being in direct contact with the surface of the heater fin gap. Preferably two or more fuses are fixed preferably into the heater fin by rivets so as to directly detect the surface temperature. A temperature detection range of 225-250°C gives the best results according to the experiments. On the other hand, metal NTCs are frequently used as thermistors. Thus, a safety member which is cost-efficient and easy-to-adjust is used.
In an embodiment of the present invention, the heat pump dryer comprises the heater fin gap which is designed flat so as to cover at most one sixth of the total surface area of the heater fin. Otherwise, deviations occur in the heat data obtained and the safety members cannot receive correct data.
In an embodiment of the present invention, the heat pump dryer comprises at least one heater fin extension which is formed by means of one or more than one cut-out on the heater fins and which bends upwards so as to make a right angle with the horizontal axis of the heater body. The highest air passage performance is provided by carrying out the design at an angle of 90 degrees so as to allow the passage of the coming process air.
In an embodiment of the present invention, the heat pump dryer comprises a protective member which is disposed on the safety member and which provides protection against environmental factors by means of a non-conductive material. Thus, the risk of short-circuit caused by fluff and fibers for safety members such as fuses is prevented.
In an embodiment of the present invention, the heat pump dryer comprises a support member whereon the heater group is positioned and which guides the process air towards the drum. By means of the support member which is preferably positioned on the rear wall of the drum, the process air is guided into the drum.
In an embodiment of the present invention, the heat pump dryer comprises a fixing member which enables the heater group to be fixed at both sides. Thus, the heater group and the support member are prevented from generating noise or vibration.
A heat pump dryer realized in order to attain the aim of the present invention is illustrated in the attached figures, where:

Figure 1 - is the representative perspective view of the dryer.
Figure 2 - is the schematic view of the dryer.
Figure 3 - is the detailed view of the dryer.
Figure 4 - is the detailed view of the heater group.
Figure 5 - is the rear perspective view of the dryer.

The elements illustrated in the figures are numbered as follows:

1. Dryer
2. Body
3. Drum
4. Fan
5. Heat pump
6. Heater wire
7. Heater support member
8. Safety member
9. Heater group
10. Heater body
11. Heater fin
12. Heater fin gap
13. Protective member
14. Heater fin extension
15. Support member
16. Fixing member

The heat pump dryer (1) comprises a body (2); a drum (3) which is provided in the body (2) and wherein the laundry is loaded; a fan (4) which is provided in the body (2) and which provides the air flow into the drum (3); a heat pump (5) which is positioned next to the fan (4); and a heater group (9) disposed on the drum (3) wall and having at least one heater wire (6) over which the process air leaving the fan (4) passes, a heater support member (7) and a safety member (8). Typically, an air flow path is followed, wherein the process air leaving the fan (4) passes over the heater group (9) to reach the drum (3), which is mostly used as open wire, and is sent back to the fan (4) after the condensation and evaporation processes in the heat pump (5). The safety member (8) generally operates like a heat sensor and serves as a mechanical switch according to the surface / ambient temperature.
The dryer (1) comprises the heater group (9) further having a heater body (10) which is designed as a metal tube and wherein the heater wires (6) therein are surrounded by resistance powder, at least one heater fin (11) which is disposed at the side of the heater body (10) and provides the heat transfer and the air passage, and a heater fin gap (12) on the heater fin (11) wherein at least one safety member (8) is disposed. Magnesium oxide is generally preferred as resistance powder. Sudden heating is prevented by means of tubular heaters compared to open wire heaters, and critical temperatures determined by the manufacturer can be detected at much lower levels by means of the safety members (8) disposed on the surface of the heater fin (11). Preferably, the heater fins (11) positioned symmetrically on both sides of the heater body (10) are provided in pairs. Moreover, in order to provide optimum heat transfer, the cross-section of the heater group (9) can be designed in the form of X, Y or I and in a wavy form. In the hybrid type dryers (1), during the heating of the process air provided by the fan (4), it is provided that the highly flammable refrigerant inside the dryer (1), which ignites at 350°C, operates in safe temperature conditions. By positioning the safety members (8) on the heater fin (11) at a distance determined by the manufacturer, inefficiencies caused by very fast response and safety problems caused by very slow response are prevented.
In an embodiment of the present invention, the heat pump dryer (1) comprises the safety member (8) which is a fuse and / or thermistor fixed by being in direct contact with the surface of the heater fin gap (12). Preferably two or more fuses are fixed preferably into the heater fin (11) by rivets so as to directly detect the surface temperature. A temperature detection range of 225-250°C gives the best results according to the experiments. On the other hand, metal NTCs are frequently used as thermistors. The NTC and the fuse can be mounted at the same point. Product safety is maximized by using both the thermal fuses and the heater fin (11) whereon the NTC is disposed.
In an embodiment of the present invention, the heat pump dryer (1) comprises the heater fin gap (12) which is designed flat so as to cover at most one sixth of the total surface area of the heater fin (11). In the experimental studies, both air permeability and heat data collection problems occur in the heater fins (11) designed by exceeding said ratio, resulting in an inefficient heater group (9).
In an embodiment of the present invention, the heat pump dryer (1) comprises at least one heater fin extension (14) which is formed by means of one or more than one cut-out on the heater fins (11) and which bends upwards so as to make a right angle with the horizontal axis of the heater body (10). By means of a molding machine, preferably more than one cut-out is formed on the heater fin (11) and the parts formed in the cut-out are bent perpendicular to the heater body (10) such that the heater fin extensions (14) are obtained. The highest air passage performance is provided by carrying out the design at an angle of 90 degrees so as to allow the passage of the coming process air.
In an embodiment of the present invention, the heat pump dryer (1) comprises a protective member (13) which is disposed on the safety member (8) and which provides protection against environmental factors by means of a non-conductive material. A large amount of fluff and fiber is generated in the dryer (1) due to the operation thereof. By insulating said fluffs and fibers, the risk of short-circuit caused by fluff and fibers for safety members such as fuses is prevented.
In an embodiment of the present invention, the heat pump dryer (1) comprises a support member (15) whereon the heater group (9) is positioned and which guides the process air towards the drum (3). The process air, which is heated by passing over the heater group (9), is guided into the drum (3) by means of the support member (15) which is generally positioned on the rear wall of the drum (3).
In an embodiment of the present invention, the heat pump dryer (1) comprises a fixing member (16) which enables the heater group (9) to be fixed at both sides. The heater group (9) and the support member (15) are prevented from generating noise or vibration due to the air flow or the movement of the drum (3).
In all the embodiments of the present invention, a riveted grounding sheet can be added on the heater group (9) to ensure electrical safety as well as thermal safety. Moreover, more sensitive results are obtained by positioning the safety members (8) adjacent to the starting point of the heater fin extensions (14) for a more accurate temperature reading.
By means of the positioning of the tubular heater group (9) and the safety member (8), the highest level of product safety is provided for heat pump dryers (1) suitable for working with environmentally-friendly gases or refrigerants.

Claims

A heat pump dryer (1) comprising a body (2); a drum (3) which is provided in the body (2) and wherein the laundry is loaded; a fan (4) which is provided in the body (2) and which provides the air flow into the drum (3); a heat pump (5) which is positioned next to the fan (4); and a heater group (9) disposed on the drum (3) wall and having at least one heater wire (6) over which the process air leaving the fan (4) passes, a heater support member (7) and a safety member (8), characterized by the heater group (9) further having a heater body (10) which is designed as a metal tube and wherein the heater wires (6) therein are surrounded by resistance powder, at least one heater fin (11) which is disposed adjacent to the heater body (10) and provides the heat transfer and the air passage, and a heater fin gap (12) on the heater fin (11) wherein at least one safety member (8) is disposed.
A heat pump dryer (1) as in Claim 1, characterized by the safety member (8) which is a fuse and / or thermistor fixed by being in direct contact with the surface of the heater fin gap (12).
A heat pump dryer (1) as in Claim 1 or 2, characterized by the heater fin gap (12) which is designed flat so as to cover at most one sixth of the total surface area of the heater fin (11).
A heat pump dryer (1) as in any one of the above claims, characterized by at least one heater fin extension (14) which is formed by means of one or more than one cut-out on the heater fins (11) and which bends upwards so as to make a right angle with the horizontal axis of the heater body (10).
A heat pump dryer (1) as in any one of the above claims, characterized by a protective member (13) which is disposed on the safety member (8) and which provides protection against environmental factors by means of a non-conductive material.
A heat pump dryer (1) as in any one of the above claims, characterized by a support member (15) whereon the heater group (9) is positioned and which guides the process air towards the drum (3).
A heat pump dryer (1) as in any one of the above claims, characterized by a fixing member (16) which enables the heater group (9) to be fixed at both sides.