US20110192579A1

US20110192579A1 - Total heat exchange element and total heat exchanger

Info

Publication number: US20110192579A1
Application number: US12/874,723
Authority: US
Inventors: Hajime SOTOKAWA; Shinya Tokizaki; Mamoru Terai; Masaru Takada
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 2010-02-09
Filing date: 2010-09-02
Publication date: 2011-08-11
Also published as: JP2011163651A; JP5506441B2

Abstract

A total heat exchange element, includes: a first flow passage through which a first airflow passes; a second flow passage through which a second airflow passes; and a partition plate that is arranged to separate the first flow passage and the second flow passage from each other and conduct total heat exchange between the first airflow and the second airflow. The partition plate has a layered structure of sandwiching a first film on both surfaces thereof with second films, the first film is a non-aqueous film having a gas shielding property and vapor-permeable property, and each of the second films is waterproof vapor-permeable film.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a total heat exchange element that conducts total heat exchange between a supply airflow and an exhaust airflow, and a total heat exchanger that comprises the total heat exchange element.
2. Description of the Related Art
One of the ventilation methods that can reduce losses in the cooling and heating efficiency of room air conditioning is ventilation between a supply airflow and an exhaust airflow. Total heat exchange, in which humidity (latent heat) as well as temperature (sensible heat) is transferred between the supply airflow and the exhaust airflow, is effective to enhance the heat exchange efficiency.
In a total heat exchange element that conducts total heat exchange, a supply airflow passage and an exhaust airflow passage are formed as independent passages with a partition plate provided therebetween. Because the total heat exchange is conducted between the supply airflow flowing in the supply airflow passage and the exhaust airflow flowing in the exhaust airflow passage, losses in the cooling and heating efficiency of room air conditioning can be suppressed by ventilating the room with a total heat exchanger containing a total heat exchange element.
As the use of total heat exchangers is spreading, total heat exchangers are introduced into environments in which condensation tends to occur due to a large difference between the temperatures of the supply airflow and the exhaust airflow, such as a cold climate, a bathroom, and a heated pool. In such environments, although condensation may not occur, the humidity is likely to increase in both the supply airflow and the exhaust airflow when the operation of the total heat exchanger starts while no air conditioning is provided in a room. This temporarily exposes the total heat exchange element to a highly humid environment. Furthermore, fog and rain water may be taken in together with air, depending on the outside weather, the conditions of the fresh-air intake, and the conditions of the arrangement of piping to the total heat exchanger, and such water may be fed into the total heat exchange element. For these reasons, a moisture-resistant partition plate is demanded for the total heat exchange element.
For example, Japanese Patent Application Laid-open No. 4-25476 discloses a total heat exchange element that includes a partition plate of a polymer porous film immersed in or coated with a hygroscopic material. As the hygroscopic material, a hydrophilic resin containing a moisture absorbent may be adopted.
In addition, Japanese Patent Application Laid-open No. 2007-285598 discloses a total heat exchange element having a partition plate that is prepared by depositing a breathable porous film on a porous base material such as nonwoven fabric and further depositing a non-aqueous hydrophilic moisture-permeable resin film having a gas shielding property on the breathable porous film.
However, according to the technology of Japanese Patent Application Laid-open No. 4-25476, because the strength of the hydrophilic resin for holding the moisture absorbent is not high enough that a large amount of moisture absorbent escapes due to the condensation that occurs on the surface of the partition plate. Thus, it is difficult to maintain the moisture permeability of the partition plate for a long period of time. This tends to degrade the performance of the total heat exchange element.
Moreover, according to the technology of Japanese Patent Application Laid-open No. 2007-285598, the non-aqueous hydrophilic resin of the partition plate is given gas-shielding and moisture-exchanging properties. In such a structure, a moisture absorbent would be added to the hydrophilic resin to enhance the moisture exchanging performance of the partition plate. However, because the dew water condensed on the surface of the partition plate is directly adhered to the hydrophilic resin, the moisture absorbent added to the hydrophilic resin is dissolved into the dew water that is adhered to the surface of the hydrophilic resin and escapes from the partition plate. Thus, the performance of the total heat exchange element is lowered when condensation occurs.
Furthermore, even if condensation does not occur, the moisture absorbent contained in the hydrophilic resin keeps absorbing a large amount of water vapor in the air under a highly humid environment so that the amount of absorbed water may exceed the water retaining capacity of the partition plate. The excess water beyond the water retaining capacity of the partition plate becomes condensed water in the hydrophilic resin and exudes to the surface of the partition plate.
The moisture absorption material in the hydrophilic resin is dissolved into the condensed water in the hydrophilic resin. When the condensed water containing the absorption material exudes to the surface of the partition plate, the absorption material of the hydrophilic resin also escapes from the partition plate. Hence, the partition plates disclosed in Japanese Patent Application Laid-open No. 4-25476 and Japanese Patent Application Laid-open No. 2007-285598 may degrade the performance of the total heat exchange element under a highly humid environment where condensation does not occur.

SUMMARY OF THE INVENTION

It is an object of the present invention to at least partially solve the problems in the conventional technology. A total heat exchange element according to an aspect of the present invention includes: a first flow passage through which a first airflow passes; a second flow passage through which a second airflow passes; and a partition plate that is arranged to separate the first flow passage and the second flow passage from each other and conduct total heat exchange between the first airflow and the second airflow, wherein the partition plate has a layered structure of sandwiching a first film on both surfaces thereof with second films, the first film is a non-aqueous film having a gas shielding property and vapor-permeable property, and each of the second films is waterproof vapor-permeable film.
The above and other objects, features, advantages and technical and industrial significance of this invention will be better understood by reading the following detailed description of presently preferred embodiments of the invention, when considered in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts an external view schematically showing an external perspective view of a structure of a total heat exchange element according to an embodiment of the present invention;

FIG. 2 depicts a traverse section showing a sectional structure of a partition plate;

FIG. 3 depicts a diagram schematically showing the structure of a heat exchanger; and

FIG. 4 depicts a table showing performance evaluation results for the total heat exchange elements of Examples 1 to 6 and Comparative Examples 1 to 10.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

An embodiment of a total heat exchange element according to the present invention is explained in detail below with reference to the drawings. This embodiment, however, should not limit the invention.

Embodiment

FIG. 1 depicts an external perspective view schematically showing a structure of a total heat exchange element according to an embodiment of the present invention. A total heat exchange element 10 includes first airflow passages (first flow passages) 4 deposited in a layered form, second airflow passages (second flow passages) 5 deposited in a layered form, sheet-like partition plates 1 for separating the passages 4 and 5 from each other, corrugated spacing plates 2 that form the passages 4 and 5 and keep a certain spacing between the partition plates 1, and an adhesive 3 that adheres the partition plates 1 to the spacing plates 2. The total heat exchange element 10 has a structure in which the flat partition plates 1 and the corrugated spacing plates 2 are alternately layered. The partition plates 1 and the spacing plates 2 are layered such that each spacing plate 2 is positioned orthogonally to its adjacent spacing plate. The first airflow passage 4 and the second airflow passage 5 are formed to be orthogonal to each other in a planar view and independent of each other.
Latent heat and sensible heat are exchanged through the medium of the partition plates 1 between a first airflow 6 flowing in the first airflow passages 4 and a second airflow 7 flowing in the second airflow passages 5. According to the present embodiment, the spacing plates 2 are shaped into corrugated sheets, but the spacing plates 2 can take any form as long as they can keep a predetermined spacing between the partition plates 1. For example, each spacing plate 2 may be prepared as a sheet folded in rectangular waves or triangular waves, or formed of multiple plate segments.
FIG. 2 depicts a traverse section showing a sectional structure of a partition plate 1. The partition plate 1, which has both a property of allowing water vapor to permeate but not air to permeate (moisture permeability) and a property of ventilating by isolating the supply airflow and the exhaust airflow from each other (gas shielding), realizes a high total heat exchange efficiency. The partition plate 1 includes a vapor-permeable non-aqueous film (first film) 12, waterproof vapor-permeable films (second films) 11 and 13, and a non-aqueous sealant (non-aqueous material) 14. The partition plate 1 has a layered structure with the waterproof vapor- permeable films 11 and 13 sandwiching the non-aqueous film 12 on both surfaces thereof.
For the non-aqueous film 12, a gas-shielding paper material containing water-soluble moisture absorbent may be adopted. The basis weight of the paper material of the non-aqueous film 12 should be 10 to 60 g/m², or preferably 15 to 30 g/m². The thickness of the paper material of the non-aqueous film 12 should be 10 to 50 micrometers, or preferably 15 to 30 micrometers. If the basis weight of the paper material is smaller than 10 g/m², or the thickness is smaller than 10 micrometers, the gas-shielding property required as the partition plate 1 is difficult to attain. If the basis weight of the paper material is greater than 40 g/m², or the thickness is greater than 40 micrometers, the temperature and humidity exchanging function may not be sufficiently delivered.
From the aspect of the moisture exchange performance of the partition plate 1, it is preferable that deliquescent salt be used for the moisture absorbent in the non-aqueous film 12. In particular, at least one of lithium chloride and calcium chloride should be adopted for the deliquescent salt to enhance the moisture exchange performance of the partition plate 1. The amount of lithium chloride or calcium chloride added to the paper material should be 2 to 10 g/m², or preferably 3 to 6 g/m², with respect to the paper material. If the amount of lithium chloride or calcium chloride that is added is smaller than or equal to 2 g/m², the vapor permeable property of the partition plate 1 is difficult to attain. On the contrary, if the amount of lithium chloride or calcium chloride that is added is greater than or equal to 10 g/m², defects tend to be caused in the production process of the partition plate 1 where the non-aqueous film 12 is sandwiched on the both surfaces thereof by the waterproof vapor- permeable films 11 and 13. Factors of causing defects will be explained later when discussing evaluation of Comparative Example 6 as a defective.
The material of the waterproof vapor- permeable films 11 and 13 that form the partition plate 1 is not particularly limited as long as it has properties of not allowing water in a liquid state to penetrate (waterproofing) but allowing water in a gaseous state to penetrate (water vapor permeability). The waterproof vapor- permeable films 11 and 13 are preferably hydrophobic films from the aspect of waterproofing, for which polyethylene, polyimide, polyurethane, polypropylene, polytetrafluoroethylene, or polysulfone may be adopted. Still more preferably, porous films made of polypropylene or polytetrafluoroethylene having the porosity of 30 to 95% may be used from the aspect of vapor permeability.
The air permeability of the waterproof vapor- permeable films 11 and 13 should be lower than or equal to 500 seconds/100 cc, or more preferably lower than or equal to 300 seconds/100 cc. The thickness of the waterproof vapor- permeable films 11 and 13 should be 5 to 100 micrometers, or more preferably 10 to 40 micrometers. If the air permeability of the waterproof vapor- permeable films 11 and 13 is higher than 500 seconds/100 cc, or the thickness is greater than 100 micrometers, the moisture exchange performance required for the partition plate 1 would be interfered.
Moreover, if the thickness of the waterproof vapor- permeable films 11 and 13 is smaller than 10 micrometers, the strength required for the partition plate 1 cannot be attained. The hydraulic resistance of the waterproof vapor- permeable films 11 and 13 should be greater than or equal to 0.1 kg/cm², or more specifically greater than or equal to 0.5 kg/cm². If the hydraulic resistance of waterproof vapor- permeable films 11 and 13 is smaller than 0.5 kg/cm², the moisture resistance of the partition plate 1 tends to decrease.
The non-aqueous sealant 14 seals the peripheral end surfaces of the partition plate 1 that forms a layered structure. The non-aqueous sealant 14 is prepared, for example, by coating the peripheral end surfaces of the partition plate 1 with a non-aqueous material such as a hot-melt adhesive. The non-aqueous sealant 14 is provided to prevent the moisture absorbent from running through the peripheral end surfaces of the partition plate 1. The material adopted for the end surface processing can be any material that is suitable for this purpose and is not particularly limited. The waterproof vapor-permeable film 11 and the waterproof vapor-permeable film 13 of the partition plate 1 may be formed of different materials.
By incorporating the partition plate 1 configured as above, the condensed water cannot reach the paper film (non-aqueous film 12) shielded by the waterproof vapor- permeable films 11 and 13, and therefore does not come into direct contact with the paper film. Thus, the water-soluble moisture absorbent added to the paper film is prevented from escaping from the partition plate 1. Furthermore, when a large mount of vapor in the air is absorbed under a special highly-humid environment where condensation does not occur, the water condensed inside the partition plate 1 can hardly escape from the partition plate because of the shielding of the waterproof vapor- permeable films 11 and 13. Thus, even if the moisture absorbent dissolves into the water condensed inside the partition plate 1, the absorbent can hardly run out of the partition plate 1 together with the condensed water. In addition, because the peripheral end surfaces of the partition plate 1 are shielded by the non-aqueous sealant 14, the moisture absorbent is prevented from escaping through the peripheral end surfaces of the partition plate 1.
By incorporating the partition plate 1 as configured above, water in the liquid state is prevented from penetrating from the outside of the partition plate 1 into the partition plate 1, and also from penetrating from the inside of the partition plate 1 to the outside of the partition plate 1. Thus, under both an environment of causing condensation and a special environment with high humidity, the water-soluble moisture absorbent is prevented from escaping from the partition plate 1.
Next, a heat exchanger comprising the total heat exchange element 10 according to the present embodiment is explained with reference to the drawings. FIG. 3 depicts a diagram schematically showing a structure of a heat exchanger 20. The total heat exchange element 10 is housed in the total heat exchanger 20. A supply airflow passage 24 that feeds the outside air into the inside of a room is formed inside the total heat exchanger 20 in such a manner as to include the first airflow passage 4 of the total heat exchange element 10. Furthermore, an exhaust airflow passage 25 that exhausts indoor air to the outside is formed inside the total heat exchanger 20 in such a manner as to include the second airflow passage 5 of the total heat exchange element 10. A supply air fan 22 is arranged in the supply airflow passage 24 to generate an airflow directed from the outside to the room. An exhaust air fan 23 is arranged in the exhaust airflow passage 25 to generate an airflow directed from the room to the outside.
When the total heat exchanger 20 is brought into operation, the supply air fan 22 and the exhaust air fan 23 are activated. Cold and dry outside air, for example, is thereby fed through the first airflow passage 4 as a supply airflow (first airflow 6), and also warm and damp room air is fed through the second airflow passage 5 as an exhaust airflow (second airflow 7). The two airflows, the supply airflow and the exhaust airflow, run through, with the partition plate 1 separating them from each other. At this point, heat is transferred between the two airflows by way of the partition plate 1, and water vapor passes through the partition plate 1. Sensible heat and latent heat are thereby exchanged between the supply airflow and the exhaust airflow. In this manner, the supply airflow is heated and humidified to be supplied to the room, while the exhaust airflow is cooled and dehumidified to be exhausted to the outside. Thus, by providing ventilation with the total heat exchanger 20, the outside and inside air can be exchanged while loss in the cooling/heating efficiency of the room air-conditioning is suppressed.
Next, the total heat exchange elements 10 of Examples 1 to 6 according to this embodiment and the total heat exchange elements 10 of Comparative Examples 1 to 10 that are introduced to compare with Examples 1 to 6 are explained.

EXAMPLE 1

In Example 1, specially-treated paper, which is treated by beating cellulose fibers (pulp) to bring the film thickness to 20 micrometers and the basis weight to approximately 20 g/m²so that gas shielding of approximately 5000 seconds/100 cc or higher can be secured, is adopted for the vapor-permeable non-aqueous film 12. Furthermore, approximately 8 g/m²of water-soluble, deliquescent lithium chloride is added as the moisture absorbent to the specially treated paper.
Porous polypropylene films having film thickness of 20 micrometers and air permeability of approximately 210 seconds/100 cc are adopted as the waterproof vapor- permeable films 11 and 13. The waterproof vapor- permeable films 11 and 13 are laminated on the both surfaces of the non-aqueous film 12 to prepare the partition plate 1.
For the spacing plate 2, one-side glazed high-quality paper that has a basis weight of approximately 40 g/m²and is corrugated is adopted. The spacing plate 2 and the partition plate 1 are adhered to each other with adhesive 3 to form a laminated unit. Thereafter, the laminated unit is shaped in such a manner that the partition plate 1 becomes approximately a square of 30 centimeters, and multiple laminated units are stacked in such a manner that the corrugations of the spacing plates 2 are orthogonally directed in an alternate manner. An approximately 50-centimeter-high total heat exchange element 10 is produced in this manner. Thereafter, the end surfaces of the passages 4 and 5 of the total heat exchange element 10 are coated with a hot-melt adhesive to seal the peripheral end surface of the partition plate 1 with the non-aqueous sealant 14.

EXAMPLE 2

In Example 2, porous polytetrafluoroethylene films having a film thickness of 22 micrometers and air permeability of approximately 0.1 seconds/100 cc are used as the waterproof vapor- permeable films 11 and 13. The rest of the structure is the same as Example 1, and thus the detailed explanation is omitted.

EXAMPLE 3

In Example 3, calcium chloride is used as a moisture absorbent that is added to the non-aqueous film 12. The rest of the structure is the same as Example 1, and thus the detailed explanation is omitted.

EXAMPLE 4

In Example 4, porous polytetrafluoroethylene films having a film thickness of 22 micrometers and air permeability of approximately 0.1 seconds/100 cc are adopted as the waterproof vapor- permeable films 11 and 13. Moreover, calcium chloride is used as the moisture absorbent added to the non-aqueous film 12. The rest of the structure is the same as Example 1, and thus the detailed explanation is omitted.

EXAMPLE 5

In Example 5, a porous polypropylene film having a film thickness of 20 micrometers and air permeability of approximately 210 seconds/100 cc is adopted as the waterproof vapor-permeable film 11. Moreover, a porous polytetrafluoroethylene film having a film thickness of 22 micrometers and air permeability of approximately 0.1 seconds/100 cc is adopted as the waterproof vapor-permeable film 13. In other words, porous films of different materials are laminated on the two surfaces of the non-aqueous film 12. The rest of the structure is the same as Example 1, and thus the detailed explanation is omitted.

EXAMPLE 6

In Example 6, calcium chloride is used as the moisture absorbent added to the non-aqueous film 12. Moreover, as the waterproof vapor-permeable film 11, a porous polypropylene film having a film thickness of 20 micrometers and air permeability of approximately 210 seconds/100 cc is adopted as the waterproof vapor-permeable film 11. Moreover, a porous polytetrafluoroethylene film having a film thickness of 22 micrometers and air permeability of approximately 0.1 seconds/100 cc is adopted as the waterproof vapor-permeable film 13. In other words, porous films of different materials are laminated on the two surfaces of the non-aqueous film 12. The rest of the structure is the same as Example 1, and thus the detailed explanation is omitted.
Next, Comparative Examples 1 to 4 are explained. In the total heat exchange elements described in Comparative Examples 1 to 4, the partition plate 1 includes films that are different from those of the Examples 1 to 6.

COMPARATIVE EXAMPLE 1

In Comparative Example 1, the partition plate 1 is formed only of the non-aqueous film 12 used in Example 1. That is, the partition plate 1 is formed by laminating the waterproof vapor- permeable film 11 or 13 on neither surface of the non-aqueous film 12. As the non-aqueous film 12, specially-treated paper to which approximately 8 g/m²of lithium chloride is added is adopted. The structure other than the partition plate 1 is the same as Example 1, and thus the detailed explanation is omitted.

COMPARATIVE EXAMPLE 2

In Comparative Example 2, the waterproof vapor-permeable film 11 is laminated on one surface of the non-aqueous film 12 of Example 1 to form the partition plate 1. Specially-treated paper to which approximately 8 g/m²of lithium chloride is added is adopted as the non-aqueous film 12. Furthermore, the porous polypropylene film of Example 1 is used as the waterproof vapor-permeable film 11. The structure other than the partition plate 1 is the same as Example 1, and thus the detailed explanation is omitted.

COMPARATIVE EXAMPLE 3

In Comparative Example 3, the waterproof vapor-permeable film 11 is laminated on one surface of the non-aqueous film 12 of Example 1, and a nonwoven fabric is laminated on the other surface. As the non-aqueous film 12, specially-treated paper to which approximately 8 g/m²of lithium chloride is added is adopted. Moreover, the porous polypropylene film of Example 1 is laminated as the waterproof vapor-permeable film 11 on one surface of the non-aqueous film. In addition, a nonwoven fabric of polyester fibers is laminated on the other side of the non-aqueous film 12. The structure other than the partition plate 1 is the same as Example 1, and thus the detailed explanation is omitted.

COMPARATIVE EXAMPLE 4

In Comparative Example 4, the end surfaces of the passages 4 and 5 of the total heat exchange element 10 are not coated with a hot-melt adhesive, and the peripheral end surface of the partition plate 1 is not sealed with the non-aqueous sealant 14. The rest of the structure is the same as that of Example 1.
Next, Comparative Examples 5 to 10 are explained. In Comparative Examples 5 to 10, the partition plate 1 is prepared to include the non-aqueous film 12, the waterproof vapor- permeable films 11 and 13 laminated on the two surfaces thereof, and the non-aqueous sealant 14, in the same manner as the above Examples, but the values indicated in the Examples are changed.

COMPARATIVE EXAMPLE 5

In Comparative Example 5, approximately 1 g/m²of lithium chloride is added to the specially-treated paper of the non-aqueous film 12. The rest of the structure is the same as Example 1, and thus the detailed explanation is omitted.

COMPARATIVE EXAMPLE 6

In Comparative Example 6, approximately 12 g/m²of lithium chloride is added to the specially-treated paper of the non-aqueous film 12. The rest of the structure is the same as Example 1, and thus the detailed explanation is omitted.

COMPARATIVE EXAMPLE 7

In Comparative Example 7, the specially-treated paper of the non-aqueous film 12 is configured to have a film thickness of 8 micrometers and a gas shielding property of approximately 2000 seconds/100 cc. The rest of the structure is the same as Example 1, and thus the detailed explanation is omitted.

COMPARATIVE EXAMPLE 8

In Comparative Example 8, the specially-treated paper of the non-aqueous film 12 is configured to have a film thickness of 60 micrometers and a gas shielding property of approximately 10000 seconds/100 cc. The rest of the structure is the same as Example 1, and thus the detailed explanation is omitted.

COMPARATIVE EXAMPLE 9

In Comparative Example 9, the porous polypropylene films that serve as the waterproof vapor- permeable films 11 and 13 are formed 3 micrometers thick. The rest of the structure is the same as Example 1, and thus the detailed explanation is omitted.

COMPARATIVE EXAMPLE 10

In Comparative Example 10, the porous polypropylene films that serve as the waterproof vapor- permeable films 11 and 13 are formed 60 micrometers thick. The rest of the structure is the same as Example 1, and thus the detailed explanation is omitted.
Next, the performances of the total heat exchange elements 10 in Examples 1 to 6 and Comparative Examples 1 to 10 are evaluated. The performance of each total heat exchange element 10 is evaluated based on the gas shielding property of the partition plate 1 and the condensation resistance of the total heat exchange element 10 with regard to the moisture exchange efficiency.
The gas shielding property of the partition plate 1 is evaluated on the basis of the evaluation of the air permeability of the partition plate 1 according to JIS P 8117 standards. In other words, how long it takes for 100-cubic-centimeter air to pass through the area of 645 square millimeters of the partition plate 1 is evaluated, and the evaluation result is used as the air permeability. Furthermore, the evaluation of the air permeability of the partition plate 1 is conducted at any given five positions of the partition plate 1. If the air permeability of the partition plate 1 is 5000 seconds or longer at each of the five positions as the result of the evaluation, the gas shielding property is judged as sufficient (o). If the air permeability of the partition plate 1 is below 5000 seconds at any of the five positions, the gas shielding property is judged as insufficient (x). The judgment of “excellent” is made only when the above conditions are met before and after the condensation test described below.
The condensation test is conducted on the partition plate 1, by repeatedly immersing the partition plate 1 in water and drying it to simulate a condensation state. The evaluation of the condensation resistance of the total heat exchange element 10 for the moisture exchange efficiency is made by evaluating the moisture exchange efficiency of the total heat exchange element 10 before and after the condensation test according to a method, which conform the double-chamber method defined in JIS B 8628 (total heat exchanger) Appendix 4, and comparing the evaluation results obtained before and after the condensation test. That is, after the moisture exchange efficiency of the total heat exchange element 10 is evaluated, a condensation test is conducted on the total heat exchanger, and the moisture exchange efficiency of the total heat exchange element 10 is evaluated again after the condensation test. As a result of the evaluations, if the moisture exchange efficiency decreases at a rate lower than 10% before and after the condensation test, the condensation resistance is judged as sufficient (o), and if the decreasing rate is greater than or equal to 10%, the condensation resistance is judged as insufficient (x).
In the evaluations of the moisture exchange efficiency, the temperature exchange efficiency, and the total heat exchange efficiency, the conditions of the primary airflow (supply airflow, the first airflow) are defined as the temperature of 27° C. and the relative humidity of 52.7% RH, and the conditions of the secondary airflow (exhaust airflow, the second airflow) are defined as the temperature of 35° C. and the relative humidity of 64.3% RH. Furthermore, the condensation test of the total heat exchange element 10 is conducted by repeatedly immersing the total heat exchange element 10 in water and then drying it to simulate the condensation state.
FIG. 4 is a table for indicating the results of the performance evaluations of the total heat exchange elements 10 in Examples 1 to 3 and Comparative Examples 1 to 10. In Comparative Example 7, for which the gas shielding property of the partition plate 1 is judged as insufficient, the evaluation of the condensation resistance in relation to the moisture exchange efficiency is not conducted.
As indicated in FIG. 4, each of the total heat exchange elements 10 of Examples 1 to 6 exhibit sufficient results in the gas shielding property of the partition plate 1, the exchange efficiency, and the condensation resistance of the total heat exchange elements 10. In addition, the total heat exchange elements 10 of Examples 1 to 6 maintain 54% or higher, which is the index of the total heat exchange efficiency of the total heat exchange element, after the condensation resistance test. This shows that they offer excellent total heat exchange performances.
Next, the factors of judgment of defects in Comparative Examples 1 to 10 are analyzed. Comparative Example 1 is judged as defective in the condensation resistance test. In Comparative Example 1, the non-aqueous film 12 is not sandwiched between the waterproof vapor- permeable films 11 and 13. For this reason, water penetrates into the specially treated paper of the non-aqueous film 12 in the condensation test, and the lithium chloride added as a moisture absorbent escapes through the two surfaces of the non-aqueous film 12 to the outside of the partition plate 1, which is considered as lowering the performance.
Comparative Example 2 is judged as defective in the condensation resistance test. In Comparative Example 2, one surface of the non-aqueous film 12 to which the lithium chloride is added is covered by the waterproof vapor-permeable film 11, while the other surface of the non-aqueous film 12 is uncovered. Because of the water penetrating into the specially treated paper, the lithium chloride added as a moisture absorbent escapes through the uncovered portion of the non-aqueous film 12 to the outside of the partition plate 1, which leads to performance degradation.
Comparative Example 3 is judged as defective in the condensation resistance test. In Comparative Example 3, one surface of the non-aqueous film 12 to which lithium chloride is added is covered by the waterproof vapor-permeable film 11, and the other surface is covered by nonwoven fabric. Because water passes through the nonwoven fabric, the water of the condensation test permeates the specially treated paper of the non-aqueous film 12. Furthermore, because of the water permeated through the specially treated paper, the lithium chloride added as a moisture absorbent escapes through the nonwoven fabric to the outside of the partition plate 1, which causes performance degradation.
Comparative Example 4 is judged as defective in the condensation resistance test. In Comparative Example 4, the two surfaces of the non-aqueous film 12 to which lithium chloride is added are covered with the waterproof vapor- permeable films 11 and 13, while the peripheral end surface of the partition plate 1 is not sealed with the non-aqueous sealant 14. For this reason, water permeates the specially treated paper to which lithium chloride is added. In addition, because of the water permeated through the specially treated paper, the lithium chloride that is added as a moisture absorbent escapes through the peripheral end surface of the partition plate 1, which can be considered as lowering the performance.
As for Comparative Example 5, favorable results are obtained in the condensation test because the two surfaces of the non-aqueous film 12 to which lithium chloride is added are covered with the waterproof vapor- permeable films 11 and 13, and the peripheral end surface of the partition plate 1 is also sealed with the non-aqueous sealant 14. However, the amount of lithium chloride added, which determines the moisture exchange performance, is smaller than the Examples, and therefore the moisture exchange performance of the total heat exchange element 10 turns out to be low.
Comparative Example 6 is judged as defective in the condensation resistance test. In Comparative Example 6, the two surfaces of the non-aqueous film 12 to which lithium chloride is added are covered with the waterproof vapor- permeable films 11 and 13, and the peripheral end surface of the partition plate 1 is sealed with the non-aqueous sealant 14. However, because the amount of lithium chloride added is greater than that of the Examples, lithium chloride tends to be precipitated on the surface of the specially treated paper. This causes unevenness to the surface of the specially treated paper, which makes the adhesion insufficient in the process of attaching it to the waterproof vapor- permeable films 11 and 13. Because of the insufficient adhesion, and also of the specially treated paper and the waterproof vapor- permeable films 11 and 13 having different rates of expansion and contraction, peeling occurs on the adhesion surfaces and the treated end surfaces. It is considered that the performance is lowered because the water in the condensation test causes the lithium chloride to escape through the peeled portions.
In Comparative Example 7, the partition plate 1 is judged that the gas shielding property is insufficient. Because the thickness of the specially treated paper of the non-aqueous film 12 is reduced, pinholes seem to be generated in the non-aqueous film 12 in the process of laminating the non-aqueous film 12 and the waterproof vapor- permeable films 11 and 13. Because of these pinholes, the paper cannot fully exert its gas shielding capacity, which results in degradation of the gas shielding performance of the partition plate 1.
In Comparative Example 8, the specially treated paper of the non-aqueous film 12 is thickened, which can be considered as posing an obstacle to the moisture exchange and lowering the moisture exchange efficiency.
Comparative Example 9 is judged to be defective in the condensation resistance test. In Comparative Example 9, the waterproof vapor- permeable films 11 and 13 made of polypropylene are thinned, and thus the strength of the waterproof vapor- permeable films 11 and 13 becomes insufficient. Because of the insufficient strength of the waterproof vapor- permeable films 11 and 13, pinholes seem to be generated in the waterproof vapor- permeable films 11 and 13 in the process of laminating the non-aqueous film 12 and the waterproof vapor- permeable films 11 and 13. Because of the pinholes, the waterproof vapor- permeable films 11 and 13 cannot fully function as waterproof films, which causes the moisture absorbent to escape and degrades the performance.
As for Comparative Example 10, the moisture exchange efficiency decreases after the condensation resistance test. Comparative Example 10 exhibits a sufficient gas shielding capability of the partition plate 1 and favorable results in the condensation resistance test. However, because the waterproof vapor- permeable films 11 and 13 are thickened, resistance components of the air produced when vapor passes through the pores of the waterproof vapor- permeable films 11 and 13 increase. This can be considered as posing an obstacle to the moisture exchange.
According to the present invention, the performance of the total heat exchange element can be prevented from being degraded even under an environment that repeatedly causes condensation or a special, highly humid environment that does not cause condensation, or even when water seeps from the outside. The total heat exchange efficiency can also be prevented from being lowered.
According to the present invention, lowering of the performance of the total heat exchanger can be suppressed when the total heat exchanger is used under an environment where condensation repeatedly occurs or under a highly humid environment even if condensation does not occur, or when water penetrates from the outside thereof. Furthermore, lowering of the total heat exchange efficiency can be also suppressed.
Although the invention has been described with respect to specific embodiments for a complete and clear disclosure, the appended claims are not to be thus limited but are to be construed as embodying all modifications and alternative constructions that may occur to one skilled in the art that fairly fall within the basic teaching herein set forth.

Claims

1. A total heat exchange element, comprising:

a first flow passage through which a first airflow passes;

a second flow passage through which a second airflow passes; and

a partition plate that is arranged to separate the first flow passage and the second flow passage from each other and conduct total heat exchange between the first airflow and the second airflow, wherein

the partition plate has a layered structure of sandwiching a first film on both surfaces thereof with second films,

the first film is a non-aqueous film having a gas shielding property and vapor-permeable property, and

each of the second films is waterproof vapor-permeable film.

2. The total heat exchange element according to claim 1, wherein the waterproof vapor-permeable film comprises porous film.

3. The total heat exchange element according to claim 2, wherein the waterproof vapor-permeable film comprises hydrophobic porous film.

4. The total heat exchange element according to claim 3, wherein the hydrophobic porous film includes at least one of polypropylene and polytetrafluoroethylene.

5. The total heat exchange element according to claim 1, wherein the non-aqueous film includes a water-soluble moisture absorbent.

6. The total heat exchange element according to claim 5, wherein the water-soluble moisture absorbent includes a deliquescent salt.

7. The total heat exchange element according to claim 6, wherein the deliquescent salt includes at least one of lithium chloride and calcium chloride.

8. The total heat exchange element according to claim 1, wherein a peripheral end surface of the layered structure of the partition plate is sealed with a non-aqueous material.

9. A total heat exchanger, comprising:

a total heat exchange element, comprising:

a first flow passage through which a first airflow passes;

a second flow passage through which a second airflow passes; and

a partition plate that is arranged to separate the first flow passage and the second flow passage from each other and conduct total heat exchange between the first airflow and the second airflow, wherein the partition plate has a layered structure of sandwiching a first film on both surfaces thereof with second films, the first film is a non-aqueous film having a gas shielding property and vapor-permeable property, and each of the second films is waterproof vapor-permeable film;

a supply air fan that generates an airflow directed from outside of a room to inside in the first flow passage; and

an exhaust air fan that generates an airflow directed from the inside to the outside in the second flow passage.