Heat Exchanger With Corrugated Heat Transfer Plates

The present invention relates generally to a heat exchanger and, more specifically, to an improved heat exchanger having a plurality of substantially parallel heat transfer plates arranged side by side at fixed intervals and each formed so as to facilitate the flow of the condensate condensed over the surface thereof along the same.

A conventional heat exchanger disclosed in Japanese Patent Application, Preliminary Publication No. 61-143697, is shown in FIGS. 6 and 7. Referring to FIGS. 6 and 7, heat transfer plates 1a, 1b and 1c each having a plurality of through holes 2 are arranged in parallel to each other at fixed intervals so as to form separate primary fluid passages A.sub.1 and A.sub.2 for passing a primary fluid A therethrough; the heat transfer plates 1a, 1b and 1c are corrugated regularly to form oblique walls 3; the primary fluid passages A.sub.1 and A.sub.2 each has alternate expanded sections 4 and narrowed sections 5; the heat transfer plates 1a, 1b and 1c are arranged side by side so that the expanded sections 4 and the narrowed sections 5 of the primary fluid passage A.sub.1 correspond to the narrowed sections 5 and the expanded sections 4 of the adjacent primary fluid passage A.sub.2, respectively; and pipes 6 for passing a secondary fluid which exchanges heat with the primary fluid therethrough penetrate through alternate lateral arrangements of the expanded sections 4 and the narrowed sections formed alternately between the heat transfer plates 1a, 1b and 1c.

When the primary fluid A flows through the primary fluid passages A.sub.1 and A.sub.2, the dynamic pressure, hence also the static pressure, of the primary fluid A varies alternately, namely, the dynamic pressure increases and the static pressure decreases in the narrowed sections 5, while the dynamic pressure decreases and the static pressure increases in the expanded sections 4. Consequently, part of the primary fluid A flows through the through holes 2 from the expanded sections 4 of the primary fluid passages A.sub.1 and A.sub.2 into the narrowed sections of the primary fluid passages A.sub.2 and A.sub.1, respectively, as indicated by arrows in FIG. 6, while the general direction of flow of the primary fluid A remains unchanged. This flow of part of the primary fluid A through the through holes 2 between the adjacent primary fluid passages A.sub.1 and A.sub.2 reduces the thickness of so-called temperature boundary layers that develop over the surfaces of the heat transfer plates 1a, 1b and 1c, which enhances the heat transfer coefficient of the heat exchanger greatly.

When the thus constructed heat exchanger is applied to an apparatus which is operated in a low temperature range, such as a refrigerator, and the temperature difference between the primary fluid and the secondary fluid which exchange heat with each other through the heat transfer plates 1a, 1b and 1c is large, or when the primary fluid which flows through the primary fluid passages is humid, the surfaces of the heat transfer plates 1a, 1b and 1c and the pipes 6 for passing the secondary fluid B become frosted. Consequently, the frost deteriorates the efficiency of heat exchange between the primary fluid and the heat transfer plates and between the primary fluid and the pipes, and narrows the primary fluid passages A.sub.1 and A.sub.2 formed between the heat transfer plates 1a, 1b and 1c to impede the flow of the primary fluid A, and thereby the heat exchanging efficiency of the heat exchanger deteriorates greatly. On the other hand, in some apparatus employing the heat exchanger, such as a refrigerator, the heat transfer plates and the pipes are heated periodically with a heater to remove the frost covering the surfaces of the heat transfer plates and the pipes of the heat exchanger. However, such an apparatus has a drawback that the water produced by defrosting the heat transfer plates and the pipes refreezes as ice over the surfaces of the heat transfer plates and the pipes.

Accordingly, it is an object of the present invention to provide a heat exchanger having improved heat transfer plates capable of facilitating the flow of the water condensate covering the surfaces of the heat transfer plates and the pipes along the same so that the surfaces of the heat transfer plates and the pipes are dried quickly to prevent the reicing of the water condensate.

According to one aspect of the present invention, guide grooves are formed in the surfaces of the heat transfer plates to facilitate the downward flow of the water condensate condensed over the surfaces of the heat transfer plates and the pipes for passing the secondary fluid therethrough.

According to another aspect of the present invention, the heat transfer plates are corrugated so that oblique walls declining from one side edge to the other side edge of each heat transfer plate are formed. The thus declined oblique walls inhibit the water condensate staying over the surfaces of the oblique walls and enhances the drying capability of the heat transfer plates.

The above and other objects, features and advantages of the present invention will become more apparent from the following description of the preferred embodiments thereof taken in conjunction with the accompanying drawings.

FIG. 1 is a front elevation of a heat exchanger, in a first embodiment, according to the present invention;

FIG. 2 is a sectional side elevation of the heat exchanger of FIG. 1;

FIG. 3 is a sectional side elevation, similar to FIG. 2, of a heat exchanger, in a second embodiment, according to the present invention;

FIG. 4 is a front elevation of a heat exchanger, in a third embodiment, according to the present invention;

FIG. 5 is a sectional side elevation of the heat exchanger of FIG. 4;

FIG. 6 is a front elevation of a conventional heat exchanger; and PG,6

FIG. 7 is a sectional side elevation of the conventional heat exchanger of FIG. 6.

In FIGS. 1 to 7, like reference characters and reference numerals designate like or corresponding parts throughout, and the description of the components and constitution of the embodiments of the present invention which are the same as the conventional heat exchanger described hereinbefore with reference to FIGS. 6 and 7 will be omitted to avoid duplication.

In a first embodiment of the present invention, a plurality of zigzag guide grooves 7 for guiding the water condensate downward are formed in the surfaces of heat transfer plates 1a, 1b and 1c so as to extend clear of through holes 2 formed in the heat transfer plates 1a, 1b and 1c, from the upper edge to the lower edge of each heat transfer plates as illustrated in FIG. 2.

In a second embodiment of the present invention, a plurality of right oblique guide grooves 7 declining to the right and a plurality of left oblique guide grooves 7' declining to the left are formed in the surfaces of heat transfer plates 1a, 1b and 1c so as to intersect each other at pipes 6 through which the secondary fluid B flows. These oblique guide grooves 7 and 7' collect and guide downward the condensate condensed over the surfaces of the pipes 6 as well as the condensate condensed over the surfaces of the heat transfer plates 1a, 1b and 1c. The constitution of the heat exchanger in the second embodiment is the same as that in the first embodiment except for the configuration of the guide grooves.

The guide grooves 7 and 7' of the heat exchangers according to the present invention facilitate the downward flow of the water condensate condensed over the surfaces of the heat transfer plates 1a, 1b and 1c and the pipes 6 and the water produced when the heat exchangers are defrosted, so that the heat transfer plates 1a, 1b and 1c and the pipes 6 are dried quickly, and thereby heat exchange between the primary fluid and the secondary fluid is achieved efficiently through the heat transfer plates.

Referring to FIGS. 4 and 5, in a third embodiment of the present invention, heat transfer plates 1a, 1b and 1c are corrugated regularly and arranged side by side similarly to those of the first and second embodiments. However, in the third embodiment, each heat transfer plate has oblique walls 3 inclining at an angle to the direction of flow of the primary fluid and declining from one side edge to the other side edge of the heat transfer plate. Therefore, the water condensate condensed over the surfaces of the heat transfer plates 1a, 1b and 1c and the pipes 6 is unable to stay over the oblique walls in flowing downward and flows obliquely downward along the oblique walls, whereby the heat transfer plate 1a, 1b and 1c are made to dry quickly.

As apparent from the foregoing description, according to the present invention, the guide grooves formed in the surfaces of the heat transfer plates or the oblique walls of the corrugated heat transfer plates facilitate the downward flow of the water condensate condensed over the surfaces of the heat transfer plates and the pipes of the heat exchanger, and thereby the heat transfer plates are made to dry quickly, and hence the heat exchanging efficiency of the heat exchanger is enhanced. Accordingly, the heat exchanger according to the present invention is effectively applicable to apparatus in which temperature difference between the primary fluid and the secondary fluid is large, such as refrigerators, and to apparatus in which the heat exchanger is exposed to a humid primary fluid.

Although the invention has been described in its preferred embodiments with a certain degree of particularity, it is to be understood that many variations and changes are possible in the invention without departing from the scope and spirit thereof.