CN115978889A

CN115978889A - Defrosting heater

Info

Publication number: CN115978889A
Application number: CN202211554355.6A
Authority: CN
Inventors: 杨欣蕾; 刘迎文; 杨鹏
Original assignee: Xian Jiaotong University
Current assignee: Xian Jiaotong University
Priority date: 2022-12-06
Filing date: 2022-12-06
Publication date: 2023-04-18

Abstract

The invention provides a defrosting heater. The defrosting heater is positioned between the evaporator and the water receiving disc and consists of two fin sleeves and electric heating wires inside the fin sleeves. The fin sleeve pipe includes the fin that integration forming relieved tooth formed on parent tube and the parent tube, and the parent tube is flat pipe, and the fin sets up in the great both sides of parent tube area to the setting of base tube is inclined to. The two sides of the base pipe with larger area face the evaporator and the water receiving tray, and the two sides with smaller area face the air duct and the box liner. The fin sleeve is made of aluminum alloy, and an oxide layer is arranged on the surface of the fin sleeve. The fin sleeve type defrosting heater provided by the invention has the advantages of compact structure, small occupied space, lower surface temperature and good defrosting capability.

Description

Defrosting heater

Technical Field

The invention relates to the technical field of refrigerators of household appliances, in particular to a defrosting heater.

Background

An air-cooled refrigerator is one type of refrigerator, and a fan is used to circulate cool air in a convection manner during refrigeration. On one hand, cold air in convection circulation continuously takes away heat of food, thereby indirectly refrigerating or freezing the food; on the other hand, the water evaporated from the food is also taken away. When cold air passes through the evaporator, moisture carried in the cold air is condensed on the surface of the pipeline and the fins of the evaporator to form a frost layer. The presence of frost deteriorates the cooling performance of the air-cooled refrigerator and even blocks the flow of air, which increases the temperature of the freezing chamber and the refrigerating chamber, and is not good for maintaining the storage quality of food. Therefore, in order to ensure the normal operation of the air-cooled refrigerator, the defrosting is required to be performed regularly.

The existing household refrigerator mostly adopts an electric heating method to defrost, and a defrosting heater can be divided into the following components according to different materials: steel tube heaters, aluminum tube heaters, and quartz tube heaters. The aluminum pipe heater has small heat productivity, usually adopts a heat conduction mode to defrost, and is complex to install; the quartz tube heater is easy to damage and short in service life, so that the steel tube heater is generally adopted in the industry at present. The steel pipe heater is usually installed between the evaporator and the water pan, and defrosting is carried out by means of natural convection and heat radiation. However, in order to avoid the excessive surface temperature of the steel tube heater, the length of the steel tube heater needs to be increased, so the steel tube heater usually needs to be arranged in double layers or even multiple layers, the total volume of the heater is large, and the space of the evaporator and the freezing chamber is squeezed.

At present, the cross section of the sleeve in the prior art is circular, and the material is steel. The heater is arranged at the lower part of the evaporator and the upper part of the water receiving tray, only about half of the radiant heat of the heater can be absorbed by the evaporator at the upper part and the water receiving tray at the lower part in the vertical direction, and the other half of the radiant heat is used for heating plastic parts in the horizontal direction. This heat is not needed for defrosting, is a waste part of the heat, and may even cause damage to nearby ducts and tanks made of plastic.

Disclosure of Invention

The invention aims to provide a defrosting heater which can effectively save occupied space and has lower surface temperature.

In order to achieve the purpose, the invention provides the following technical scheme: the defrosting device comprises an evaporator, a water receiving disc and a fin sleeve defrosting heater positioned between the evaporator and the water receiving disc, wherein the fin sleeve defrosting heater consists of two fin sleeves and an electric heating wire arranged in the fin sleeves; the fin sleeve comprises a base pipe and fins formed by integrated relieved teeth on the base pipe.

The base tube is a flat tube, and the fins are arranged on two sides of the base tube with larger area and are inclined to the base tube.

The two sides of the base pipe with larger area face the evaporator and the water pan, and the two sides of the base pipe with smaller area face the air duct and the box liner.

The spacing F of the fins _d Not less than 5 mm, height F of said fin _h No more than 6 mm, and the included angle alpha between the fin and the base tube is within the range

The width W of each fin sleeve is not more than one third of the width W of the evaporator 1.

The two fin sleeves are arranged on the same horizontal plane, and the distance between the two fin sleeves

The fin sleeve is characterized in that the left side and the right side in the fin sleeve are respectively embedded with an electric heating wire which are connected in parallel, sealing glue and insulating glue on the outer side are arranged at two ends of the fin sleeve, a conductive rod which penetrates through the sealing glue and the insulating glue to be connected with the electric heating wires is further arranged at the rear end of the fin sleeve, and a heat-conducting medium is filled between the electric heating wires and the fin sleeve.

The fin sleeve is made of aluminum alloy, and an oxide layer is arranged on the surface of the fin sleeve.

And the lower parts of the end plates at two sides of the evaporator are respectively cut with two rectangular holes which are matched with the fin sleeves.

Compared with the prior art, the invention has the following advantages:

in order to ensure that the heater can still be defrosted by means of natural convection and heat radiation under the condition of low surface temperature, on one hand, fins formed by integrated shovel teeth are additionally arranged outside a sleeve of the heater, the outer surface area of the heater is greatly increased, so that more air can be heated to rise and melt a frost layer on the surface of the evaporator, and the natural convection is strengthened.

Furthermore, the surface of the heater is subjected to oxidation treatment, the surface emissivity is increased, and meanwhile, compared with a round pipe, the flat pipe and the inclined fins are used for optimizing a radiation heat transfer path, so that radiation heat exchange among the heater, the evaporator and the water pan is enhanced. The fin sleeve defrosting heater provided by the invention is made of aluminum alloy, and the specific heat capacity is larger than that of steel, so that the surface temperature of the heater can be ensured not to be too high when the power per meter is larger, the length of a heating pipe can be shortened, the multilayer design of the steel pipe heater provided by the prior art is changed into a single layer, the occupied upper and lower spaces are reduced, and the saved space can be used for increasing the volume of an evaporator or increasing the available volume of a freezing chamber.

In conclusion, the defrosting heater provided by the invention has the advantages of compact structure, small occupied space and low surface temperature, avoids scorching and damage of plastic parts near the heater, and can ensure good defrosting capability.

Through experimental tests, the maximum temperature of the surface of a 250W steel pipe heater provided by the prior art in the defrosting process is 212 ℃, and the maximum temperature of a 270W defrosting heater provided by the invention is 126 ℃. Meanwhile, the defrosting time of the steel tube heater is 23 minutes, and the defrosting time of the defrosting heater provided by the invention is 18 minutes. The finned sleeve defrosting heater provided by the invention can ensure good defrosting capability under the conditions of reducing surface temperature and volume.

Drawings

FIG. 1 is a schematic distribution diagram of a finned sleeve defrosting heater, an evaporator and a water pan provided by the invention;

FIG. 2 is a schematic view of a partial structure of a fin sleeve defrosting heater provided by the invention;

FIG. 3 is a schematic view of a longitudinal section structure of a fin sleeve defrosting heater provided by the invention;

FIG. 4 is a schematic view of the connection of the finned tube defrosting heater and the evaporator provided by the invention;

FIG. 5 is a schematic view of the radiative heat transfer between two objects;

FIG. 6 is a schematic view of a radiation surface of a fin sleeve defrosting heater provided by the invention;

FIG. 7 is a graph comparing the performance of a finned tube defrosting heater according to the present invention and a heater according to the related art;

FIG. 8 is a graph of the surface temperature of a fin sleeve defrosting heater provided by the present invention;

in the figure: 1. an evaporator; 2. the fin sleeve defrosting heater comprises: 21. fin sleeve: 211. a base pipe; 212. a fin; 213. a first radiation surface; 214. a second radiation surface; 215. a third radiating surface; 216. a fourth radiating surface; 22. an electric heating wire; 23. a heat conducting medium; 24. sealing glue; 25. insulating glue; 26. a conductive rod; 3. a water pan; 4. an evaporator end plate; 5. an object to be heated; 6. a heating element.

Detailed Description

The present invention will be described in further detail below with reference to the accompanying drawings.

Referring to fig. 1, the present invention comprises an evaporator 1 and a water collector 3, and a fin sleeve defrosting heater 2 between the evaporator 1 and the water collector 3.

Referring to fig. 2, the fin sleeve defrosting heater 2 of the present invention is composed of two fin sleeves 21 and an electric heating wire 22 inside the fin sleeves 21. An electric heating wire 22 is respectively embedded at the left side and the right side in the fin sleeve 21, and a heat-conducting medium 23 is filled between the electric heating wire 22 and the fin sleeve 21. The heat transfer medium 23 may be selected from magnesium oxide powder. All the electric heating wires 22 are connected to a power supply in parallel. The fin sleeve 21 includes a base pipe 211 and fins 212 formed as integral relieved teeth. In order to ensure that the fin sleeve defrosting heater provided by the invention can still defrost by means of natural convection and heat radiation under the condition of low surface temperature, the outside of the sleeve of the heater is provided with fins formed by integrated relieved teeth. The base pipe 211 is a flat pipe, and the fins 212 are disposed on two sides of the base pipe 211 having a large area and inclined to the base pipe 211. The two sides of the base pipe 211 with larger area face the evaporator 1 and the water pan 3, and the two sides of the base pipe 211 with smaller area face the air duct and the box liner.

Referring to fig. 3, two ends of the fin sleeve 21 of the present invention need to be sealed, including a sealant 24 and an insulating glue 25 on the outer side, and a conductive rod 26 penetrating through the sealant 24 and the insulating glue 25 and connected to the electric heating wire 22 is further disposed at the rear end of the fin sleeve 21. After the electric heating wire 22 is electrified, the temperature rises, and the heat is transferred to the outside fin sleeve 21 through the heat conduction of the heat-conducting medium 23, so that the surface temperature of the fin sleeve 21 rises, and then is transferred to the surfaces of the evaporator 1 and the water pan 3 through natural convection and radiation, and the defrosting effect is realized.

Referring to fig. 4, the two fin tubes 21 of the present invention are installed at the same level. In order to ensure that wind energy smoothly flows into the evaporator 1 through the defrosting heater, the width W of each fin sleeve 21 is not more than one third of the width W of the evaporator 1. A certain distance d should be maintained between the two fin tubes 21 to ensure that the wind passes between them, while, for even heating of the evaporator, it is preferable,

two rectangular holes are cut in the lower portions of the end plates 4 on the two sides of the evaporator 1, and the two ends of the fin sleeve defrosting heater 2 are respectively embedded in the rectangular holes, so that the fin sleeve defrosting heater 2 can be stably installed on the lower portion of the evaporator 1.

The fin sleeve 21 is made of aluminum alloy, for example, aluminum 6063, and the material can avoid material accumulation and cutter sticking caused by over-soft material and fin cracking caused by over-hard material in the scraping process, and has excellent corrosion resistance. The surface of the fin collar 21 is subjected to oxidation treatment and has an oxide layer. The emissivity of the metal surface after oxidation treatment is greatly increased. The defrosting heater 02 provided by the prior art is usually made of steel, and the specific heat capacity of the aluminum alloy is larger than that of the steel, so that when the power per meter of the fin sleeve defrosting 2 heater provided by the invention is larger, the surface temperature of the heater can be ensured not to be too high, the length of a heating pipe can be shortened, and the volume of the defrosting heater can be reduced.

First, the present invention analyzes the advantages of a fin-in-tube defrosting heater from a natural convection perspective.

According to the fin sleeve defrosting heater 2 provided by the invention, the external surface area of the defrosting heater is greatly increased due to the existence of the fins 212. Compared with a steel pipe defrosting heater, the fin sleeve defrosting heater 2 has a larger contact area with the air at the bottom of the evaporator 1. And parent tube 211 and fin 212 integrated into one piece, body heat dissipation can be realized to fin sleeve 21, and parent tube 211 almost does not have the difference in temperature with fin 212, therefore fin sleeve pipe defrosting heater 2 can fully effectively get heated air, makes more air be heated and rises for the speed of melting on the frost layer on evaporimeter 1.

Second, the advantage of the fin-in-tube defrost heater was analyzed from a thermal radiation perspective.

As known from the basic concept of heat transfer, the amount of radiant heat between two surfaces at any position is related to the solid angle between the two surfaces. As shown in fig. 5, assuming that an object 5 to be heated is located at the upper side and a heating body 6 is located at the lower side, the radiation heat exchange between the two object surfaces can be decomposed into an integral value of the radiation heat exchange amount between an infinite number of minute surfaces, and the radiation heat exchange amount between any two minute surfaces of the two object surfaces is positively correlated with the cosine of the included angle θ between the two minute surfaces, that is, the larger the included angle between the two minute surfaces is, the worse the radiation heat exchange effect is, so that the radiation heat exchange amount between the two object surfaces is also smaller. Meanwhile, the theory can also know that when the included angles between all the tiny surfaces of the two heaters and the heated object are the same, the larger the surface area of the heater is, the larger the total radiation heat exchange quantity between the two surfaces is, and the better the heating defrosting effect is.

In the fin-in-tube defrosting heater 2 provided by the invention, the evaporator 1 can absorb the radiant heat of four surfaces, namely a first radiant surface 213, a second radiant surface 214, a third radiant surface 215 and a fourth radiant surface 216 in fig. 6, and the included angle alpha between the fin 212 and the base tube 211 is 60 degrees as schematically illustrated. The included angle between the first radiation surface 213 and the second radiation surface 214 and the evaporator 1 is 0 degree, and the radiation heat exchange effect between the two surfaces and the evaporator 1 is the best; the third radiation surface 215 forms an angle of 30 degrees with the evaporator 1; the fourth radiation surface 216 has a larger included angle with the evaporator 1, the radiation heat exchange effect between the surface and the evaporator 1 is poorer, but the surface has the largest surface area, and the radiation heat with smaller area can be compensated. The analysis process for the water pan 3 at the lower part of the fin sleeve defrosting heater 2 is the same as that of the upper evaporator 1. In conclusion, because the included angle between the evaporator and the heater is reduced, and the surface area of the heater is increased, the radiation heat transfer path is optimized, the radiation heat absorbed by the evaporator and the water pan is larger, and the defrosting effect is better. The area of the top of the heater 2 is about 5 times larger than that of the side part, so that the small radiation heat received by the air channel and the box liner of the side part can be ensured, and the damage caused by high temperature is avoided.

It should be noted that if the fins 212 are spaced at a distance F _d Too small, fin 212 height F _h Too high or too small an angle α between the fin 212 and the tube 211 will cause the projections of the fin 212 on the plane of the tube 211 to overlap, resulting in the disappearance of the second radiation surface 214 and the increase of the angle between the fourth radiation surface 216 and the evaporator 1, which is not favorable for heat radiation. Preferably, the fins 212 are spaced apart by a distance F _d Not less than 5 mm, height F of fin 212 _h The included angle alpha between the fins 212 and the base tube 211 is within the range of 6 mm:

compared with the prior art, the invention has the following advantages:

the fin sleeve defrosting heater provided by the invention is made of aluminum alloy, and the specific heat capacity is larger than that of steel, so that the surface temperature of the heater can be ensured not to be too high when the power is higher, the length of a heating pipe can be shortened, the multilayer design of the steel pipe heater provided by the prior art is changed into a single layer, the occupied upper and lower spaces are reduced, and the saved space can be used for increasing the volume of an evaporator or increasing the available volume of a freezing chamber.

In order to ensure that the heater can still be defrosted by means of natural convection and heat radiation under the condition of low surface temperature, on one hand, fins formed by integrated shovel teeth are added outside a sleeve of the heater, the external surface area of the heater is greatly increased, so that more air can be heated to rise and melt a frost layer on the surface of an evaporator, and the natural convection is strengthened. On the other hand, the surface of the heater is oxidized to increase the surface emissivity. Meanwhile, compared with a round pipe, the flat pipe and the inclined fins are used for optimizing a radiation heat transfer path, so that radiation heat exchange among the heater, the evaporator and the water pan is enhanced.

The defrosting performance of the 250W defrosting heater provided by the related art and the defrosting performance of the 270W fin sleeve defrosting heater provided by the invention are respectively tested through experiments. Fig. 7 shows the defrost time and the freezer temperature rise during defrost for both types of heaters. It can be found that the defrosting time of the defrosting heater provided by the related art is 23 minutes, and the defrosting time of the defrosting heater provided by the invention is 18 minutes. And the shorter defrosting time ensures that the temperature rise of the freezing chamber is smaller during defrosting, thereby shortening the subsequent temperature recovery period. For the whole defrosting and the recovery period thereof, the finned sleeve defrosting heater provided by the invention shortens the consumed time by 14 minutes and reduces the power consumption by 10.4%. Fig. 8 shows the surface temperature of the fin-in-tube defrosting heater during defrosting, with a maximum temperature of only around 130 c. Therefore, the fin sleeve defrosting heater provided by the invention can ensure good defrosting capability under the conditions of reducing the surface temperature and reducing the volume.

Claims

1. A defrosting heater is characterized in that: the defrosting device comprises an evaporator (1), a water pan (3) and a fin sleeve defrosting heater (2) positioned between the evaporator (1) and the water pan (3), wherein the fin sleeve defrosting heater (2) consists of two fin sleeves (21) and an electric heating wire (22) arranged inside the fin sleeves (21); the fin sleeve (21) comprises a base pipe (211) and fins (212) which are formed by integrally forming relieved teeth on the base pipe (211).

2. The defrosting heater of claim 1, wherein the base pipe (211) is a flat pipe, and fins (212) are arranged on both sides of the base pipe (211) with a larger area and are arranged obliquely to the base pipe (211).

3. The defrosting heater according to claim 2, wherein the two sides of the base pipe (211) with larger area face the evaporator (1) and the water pan (3), and the two sides of the base pipe (211) with smaller area face the air duct and the tank.

4. Defrosting heater according to claim 1 characterized in that the spacing F of the fins (212) _d Not less than 5 mm, height F of said fins (212) _h Not more than 6 mm, the included angle alpha between the fins (212) and the base pipe (211) is within the range of

5. The defrosting heater according to claim 1 characterized in that the width W of each fin sleeve (21) is not more than one third of the width W of the evaporator (1).

6. The defrosting heater of claim 5, wherein the two fin sleeves (21) are installed on the same horizontal plane, and the distance between the two fin sleeves (21)

7. The defrosting heater according to claim 1, wherein the left side and the right side of the inside of the fin sleeve (21) are respectively embedded with an electric heating wire (22) which is connected in parallel, both ends of the fin sleeve (21) are respectively provided with a sealant (24) and an insulating glue (25) at the outer side, the rear end of the fin sleeve (21) is also provided with a conductive rod (26) which passes through the sealant (24) and the insulating glue (25) and is connected with the electric heating wire (22), and a heat-conducting medium (23) is filled between the electric heating wire (22) and the fin sleeve (21).

8. The defrosting heater of claim 1, wherein the fin collar (21) is made of aluminum alloy and has an oxide layer on the surface.

9. The defrosting heater according to claim 1, characterized in that the lower part of the end plate (4) on both sides of the evaporator (1) is cut with two rectangular holes adapted to the fin sleeves (21).