JPH0443756Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Field of Industrial Application) The present invention relates to a cross-fin type air heat exchanger used in heat pump type air conditioners and the like.

(Prior Art) As a conventionally known cross-fin type air heat exchanger, there is one that has multiple rows of refrigerant systems 3a', 3b', and 3c' from the windward side to the leeward side, as shown in FIG. (For example, see Japanese Patent Application Laid-open No. 13247/1983). In the air heat exchanger having such a structure, the heat transfer tubes 2a', which constitute the refrigerant systems 3a', 3b', 3c',
Tubes having the same heat transfer performance are used as 2b', 2c', and these heat transfer tubes 2a', 2b', 2
Common fins 1', 1', . . . are arranged perpendicularly to c'.

(Problem to be solved by the invention) When the air heat exchanger of the above-mentioned known example is used as an outdoor coil of a heat pump type air conditioner, this outdoor coil acts as an evaporator during heating operation, and the outside air temperature When the temperature decreases, the fin surface temperature becomes 0° C. or lower and frost formation d' occurs. This frost d' advances from the fin surface located on the upstream side (i.e., windward side) with respect to the air flow W', and as the amount of frost increases, the fin surface becomes Clogging occurs on the windward side of tubes 1' and 1', resulting in an increase in ventilation resistance and a decrease in air volume. As a result, the refrigeration capacity is drastically reduced, making it impossible to maintain normal operation as a refrigeration system. Therefore, when the amount of frost exceeds a certain limit, defrosting operation using a reverse cycle method or the like in which the refrigerant flow path is reversed becomes necessary. During this defrosting operation, cold air is blown toward the interior of the room, causing discomfort due to cold draft, and when the frequency of defrosting operation increases, a problem arises in that the average heating capacity decreases.

This invention was made in view of the above points,
The purpose of this invention is to delay as much as possible the occurrence of clogging of the fins due to frost formation in a cross-fin type air heat exchanger.

(Means for Solving the Problems) In the present invention, as a means for solving the above problems, as shown in Figures 1 to 3, the refrigerant system is arranged in three rows from the windward side to the leeward side. 3a, 3
In the cross-fin type air heat exchanger having the refrigerant systems 3a, 3b, 3c, the heat exchanger tubes 2a are made of smooth inner surfaces, and the inner surfaces are formed with spiral corners 4, 4, . . . with a helical angle of θ _1. Heat exchanger tube 2b made of a processed tube and a helical angle θ ₂ smaller than the helical angle θ ₁
Each of the heat exchanger tubes 2c is made of an internally processed tube with a spiral spiral 5, 5... formed on the inner surface thereof, and is orthogonal to the heat exchanger tubes 2a, 2b, 2c and is connected to these heat exchanger tubes 2a, 2b, 2c. Commonly used fins 1, 1, . . . are provided.

(Function) In the present invention, the following effects can be obtained by the above-mentioned means.

That is, even if the evaporation temperature is the same, the heat exchanger tubes 3a,
The tube outer surface temperatures Ta, Tb, and Tc (see Fig. 4) of tubes 3b and 3c gradually decrease from the windward side to the leeward side (that is, Ta〉Tb〉Tc), and the air temperature and heat transfer tube outer surface temperature (in other words, Then, the temperature difference from the fin surface temperature will be the same from the windward side to the leeward side.
Therefore, frost buildup on the fins progresses uniformly regardless of whether they are on the windward side or the leeward side, and the time until clogging occurs due to frost formation becomes longer.

(Embodiments) Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

An embodiment of the invention is shown in FIGS. 1 and 2. FIG.

The air heat exchanger of this embodiment is of a cross-fin type having a complicated row of refrigerant systems 3a, 3b, and 3c from the windward side to the leeward side with respect to the air flow W. Refrigerant is distributed to each of the refrigerant systems 3a, 3b, and 3c via a flow divider 7.

The heat exchanger tubes 2a, 2b, 2c constituting the refrigerant systems 3a, 3b, 3c, respectively, have second
As shown in the figure, these heat exchanger tubes 2a, 2b, 2c
A large number of fins 1, 1, . . . which are commonly used are arranged orthogonally.

The heat exchanger tubes 2a, 2b, and 2c are each a smooth tube with a smooth inner surface, an inner-surface-treated tube having spiral courses 4, 4, etc. formed on the inner surface with a helical angle θ ₁ (approximately 25° in this embodiment), and Helix angle θ ₂ : Approximately 18° in this example)
An internally processed pipe is used in which spiral grooves 6, 6, . . . are formed on the inner surface.

In other words, the heat transfer tubes 2a, 2b, and 2c are constructed of tube bodies that have relatively higher heat transfer performance on the leeward side than on the windward side. Incidentally, the helical angle θ of the spiral in an internally machined pipe with a spiral
The change in the refrigerant side heat transfer coefficient k with respect to the temperature is as shown in FIG. According to this, as the helical angle θ increases, the refrigerant side heat transfer coefficient k decreases.

The air heat exchanger having the above structure operates as follows.

When using this air heat exchanger as an outdoor coil of a heat pump type air conditioner, the heat exchanger tube 2a,
As the heat transfer performance of 2b and 2c gradually increases, their tube outer surface temperatures (in other words, fin surface temperatures) Ta, Tb, and Tc gradually decrease, and as a result, the air temperature and fin surface temperature decrease. The temperature difference between the windward and windward sides is almost the same. Therefore, the progress of frost formation on each fin 1, 1, . . . is made uniform, and the time until clogging occurs due to frost formation d is lengthened. In other words, there is less decline in performance during frost formation, and
The frequency of defrosting operations also decreases, and the average heating capacity improves.

(Effects of the invention) As described above, according to the invention, in a cross-fin type air heat exchanger having three rows of refrigerant systems 3a, 3b, and 3c from the windward side to the leeward side, the refrigerant systems 3a, 3b and 3c are a heat exchanger tube 2a made of a smooth inner surface tube, a heat exchanger tube 2b made of _an inner surface processed tube with spiral corners ₄ , 4, _. Spiral course 5,
Each of the heat exchanger tubes 2c is made of an inner-processed tube with 5... formed on the inner surface, and a fin fin is orthogonal to the heat exchanger tubes 2a, 2b, 2c and shared by these heat exchanger tubes 2a, 2b, 2c. Since heat exchanger tubes 3a, 3... are arranged, heat exchanger tubes 3a, 3
Since the tube outer surface temperatures Ta, Tb, and Tc of tubes b and 3c gradually decrease from the windward side to the leeward side, the temperature difference between the air temperature and the fin surface temperature is almost the same on the windward and leeward sides, and the fin 1 , 1... will progress uniformly. Therefore, the reduction in air volume due to frost formation is extremely small, and the time until clogging occurs due to frost formation is lengthened. This contributes to a significant reduction in the frequency of defrosting operations when used as an outdoor coil in a heat pump air conditioner for heating operation at low outside temperatures, contributing to an improvement in the average heating capacity and coefficient of performance. It's a big deal.

In addition, the fins 1, 1... are connected to the heat transfer tubes 2a, 2b, 2
Since it is shared with respect to c, there is also the advantage that it is possible to reduce costs and make it more compact by sharing parts.

[Brief explanation of the drawing]

Fig. 1 is a side view schematically showing an air heat exchanger according to an embodiment of the present invention, Fig. 2 is a sectional view of the main part of the air heat exchanger of Fig. 1, and Fig. 3 is a spiral plan view. FIG. 4 is a characteristic diagram showing the change in the refrigerant side heat transfer coefficient k with respect to the helical angle θ of the spiral in the inner surface processed pipe, and FIG. FIG. 5, a characteristic diagram showing temperature, air temperature, and evaporation temperature, is a sectional view of a main part of a conventional air heat exchanger. 2a, 2b... Heat exchanger tube, 3a, 3b... Refrigerant system.

Claims (1)

[Scope of utility model registration request] Refrigerant system 3 in three rows from the windward side to the leeward side
In the cross-fin type air heat exchanger having the refrigerant systems 3a, 3b, 3c,
A heat exchanger tube 2a made of a smooth inner surface, a heat exchanger tube 2b made of _an inner surface processed tube having spiral grooves ₄ , ₄ , . Each of the heat exchanger tubes 2c is made of an inner-processed tube with 5, 5, . An air heat exchanger characterized in that fins 1, 1... are arranged.