EP0030863A1

EP0030863A1 - An exchange element for a heat and/or moisture exchange and an exchanger for heat and/or moisture

Info

Publication number: EP0030863A1
Application number: EP80304523A
Authority: EP
Inventors: Haruo Naganuma
Original assignee: HEI CO Ltd
Current assignee: HEI CO Ltd
Priority date: 1979-12-14
Filing date: 1980-12-15
Publication date: 1981-06-24
Also published as: AU6535580A; CA1144148A; JPS5687417A

Abstract

A heat and/or moisture exchange element comprises a laminated structure of a hygroscopic-agent-impregnated exchanging menber (6) comprising a base paper (4) made by mixing synthetic pulp having a water-repellant and thermo-plastic properties to provide a shape retaining moisture resistant base with fibre basic material and further by coating the above mentioned mixed paper with abrasion-resistant in the end face of the exchangeing member. The layers (4) of the member are corrugated and the laminate consists of rings of the layers forming a drum-shaped element for mounting in a drum shaped housing (10) of a heat exchanger.

Description

This invention relates to an exchanging member for heat and/or moisture and, more particularly, to an exchanging member of which form and shape can be maintained solid and firm even when such a member is subjected to moisture by the hygroscopic agent impregnated therein.
In the prior art, there has been provided the moisture exchange for a rotary dehumidifier as this type of exchanger. In the moisture-exchanger of the above mentioned type, the basic paper usually made with asbestos fibre is corrugated, then laminated to form a so-called asbestos fibre lamination and impregnated with a hygroscopic agent such as lithium chloride or the like. As shown in Figure 1, a moisture exchanger of this type 1 is housed in a rotary 2 of the drum shape which rotates at a low speed. Air A to be processed is fed from one side of the said rotary 2 to the other side thereof to be dehumidified and to become dried air using a portion of the moisture exchanger 1. Using the other portion of the moisture exchanger 1, regeneration air C which has been heated by a heater 3 is fed from the other side of the rotary 2 to the first side thereof to become regenerated exhaust air D and taking up the moisture which has been absorbed in the moisture exchanger 1. Although the moisture exchanger 1 is dried and regenerated by the regeneration air C, it is constantly subjected to the moisture; thereby the laminated structure tends to disintegrate to the stage of destruction thereof in the end. The aforementioned problem is not limited to such a moisture exchanging member 1, but is universally encountered in other types of exchangers such as an exchanger between moisture and heat or a heat exchanger which is impregnated with a hygroscopic agent.
In order to solve such detrimental problems, there has heretofore been provided a process wherein several chemically active inorganic substances, for instance, water glass, are impregnated in a moisture exchanger member 1 in a form of an aqueous dispersion to form insoluble deposited substances which are used as lamination frames reinforcing the structures thereof._However, in such a case, the above mentioned process required various additional steps such as the step of impregnating the water glass with aqueous dispersion, the step of impregnating water glass with other aqueous dispersion in order to make the water glass insoluble salts and the step of drying, thus complicating the whole manufacturing process.
The present invention aims at providing an exchanger for heat and/or moisture free of above mentioned conventional technical problems and such an object of the present invention is achieved by using as the basic paper made by mixing synthetic pulp having water repellant and thermo-plastic properties with the basic fibre material and by coating the said mixed paper with abrasion resistant material in the end face of the exchanger . member.
The invention provides an exchange element for a heat and/or moisture exchanger comprising a laminate of layers of a base paper formed from a low melting point, water repellant thermo-formable synthetic pulp having a hygroscopic agent impregnated therein, the layers of the laminate being thermo-formed with corrugations whereby air spaces are provided between adjacent layers.
The invention, further provides a laminated structure of a base paper made with synthetic pulp having water repellant and thermo plastic properties and having a low melting point which is thermo-formed into a corrugated form and further laminated, and a hygroscopic agent which is impregnated in the said laminated structure, the structure being housed inside a rotor of a drum shape.
More specifically the laminated structure may be made of a base paper with a synthetic pulp having water repellant and thermo-plastic properties and having a low melting point which is thermo-formed into a corrugation and further laminated, a hygroscopic agent impregnated into said paper and an abrasion resistant material may be coated over said basic paper in the end face of the laminated structure.
The following is a description of one embodiment of the invention reference being made to the accompanying drawings in which:

Figure 1 is a schematic view explaining a rotor type dehumidifier.
Figures 2 and 3 show an embodiment according to the present invention wherein Figure 2 is a frontal view of the exchanger in the state it is housed inside of the rotor while Figure 3 is a cross-sectional view along the line III-III of Figure 2.,

A basic paper to be used in the present invention is structured by mixing synthetic pulp of a low-melting point such as polyethylene, nylon, acryl, polyester, polypropylene or the like which has little hygroscopic property but has both a water repellant property and a thermo-plastic property on a base material of such fibres as asbestos fibre, cellulose fibre, glass fibre, carbon fibre, ceramic fibre or the like. The above mixed paper is first corrugated and then laminated to form a concentric ring laminated structure 5 as shown in Figure 2. In this case the mixed base paper 4 is thermo-formed in a form of corrugation, therefore, the synthetic pulp which has been deformed by the thermoform between the base fibre material supports the corrugated form of the mixed base paper and further the excellent.water repellant property and structure stability of the synthetic pulp enforces inter-fibre strength and stabilises the lamination structure even under a moist condition. The laminated structure 5 is impregnated with a hygroscopic agent such as lithium chloride, lithium bromide, silica gel, activated alumina, molecular sieves or the like and the impregnation therefor may be conducted at any stage during the manufacture of the base paper 4, either at a step before laminating the base paper 4 or at a step after laminating the structure 5. The corrugations of the layers create 'air spaces between adjacent layers through which air to be processed can pass.
The mixing rate of synthetic pulp and inter-fibre strength after thermoforming and under the moist conditions are substantially proportionate to each other. The relative strength compared to a water-proof paper are listed in the table below. In the table, each sample paper weighs 80 g/m² and NBKP in the composition column indicates coniferous tree breached draft pulp, NUKP coniferous tree unbreached kraft pulp, LBKP hardwood breached pulp and synthetic pulp polyethylene respectively.
The moisture exchanging capacity of the exchanging member, on the other hand, varies depending on the amount of free space existing between the base fibers (i. e. the amount of the impregnated hygroscopic agent). Therefore, the mixing rate of the synthetic pulp is limited at its maximum so as to secure such a free space.
When considering both the inter-fiber strength and the inter-fiber free space in the mixed base paper, the optimal ratio therebetween is that the synthetic pulp is 20 to 40% and more preferably about 30% of the base paper in terms of weight for an exchanging member for the moisture. In the case of an exchanging member for heat, the ratio may be slightly bigger than the above.
Since the chemical substance such as urea or a phospheric compound improves flame resistance or shrink resistance,dimensional stability is enhanced by impregnating such agents, thus further improving stability of structure. In the embodiment of the present invention, such an agent is impregnated together with the hygroscopic agent.
The exchanging member structure and process in the aforementioned manner is housed in a rotor 2 either in the form of a cylinder or a radially sectioned form.
As shown by the two-dot chain line in Fig. 3, since a seal 6 is provided in the main body of a casing (not shown) which supports rotatively the rotor 2 so as to separate the process air A from the regeneration air C, the end face of the exchanging member 5 constantly contacts in a slidable manner with the seal 6. In order to prevent damage which might be caused by above slidable contact therebetween, the area 7 on the end face which is encircled by a broken line in Fig. 3 is coated with abrasion resistent substance such as a rigid resin. By coating in such a manner, the contacting point with the seal 6 is hardened free of damages. It further reinforces the laminated structure to improve moldability under moist condition. The coating with such abrasion resistent substance may be given on the mixed base paper 4 after thermoforming or may be given thereon when laminated. But when coating on-the laminate it is necessary to provide some measure not to close the free space between laminated layers. Due to the coating, the end face 7 of the exchanging member 1 may become unable to absorb moisture but such coated area is so small that reduction in moisture absorptive capacity is negligible. In Figs. 2 and 3, the reference number 8 denotes a rotating axis of the rotor 2, 9 and reinforcing rib, 10 a rim and 11 a pressing plate.
As explained in the foregoing reference made to the embodiment, the exchanging member according to the present invention is structured by thermoforming a mixed base paper which is made by mixing synthetic thermo pulp of a low melting point having plasticity but not much hygroscopic property on base fiber material, thereby the laminated structure can be retained even under moist condition because of the rigidity .and water repellent property of synthetic pulp. Since the base paper itself has a capacity to retain the laminated structure, this method is advantageous in that it can eliminate additional steps such as impregnating water glass heretofore required and that it can simplify the manufacture. By coating the end face of the exchanging member alone, it can achieve a higher resistance against the seal as well as enhance stability of the lamination structure without deteriorating the hygroscopic water thereof.

Claims

1. An exchange element for a heat and/or moisture exchanger comprising a laminate of layers of a base paper formed from a low melting point, water repellant thermo-formable synthetic pulp having a hygroscopic agent impregnated therein, the layers of the laminate being thermo-formed with corrugations whereby air spaces are provided between adjacent layers.

2. An exchange element as claimed in claim 1 wherein the synthetic pulp comprises any one of the following: polyethylene, nylon, acryl, polyester, polypropylene.

3. An exchange element as claimed in claim 1 or claim 2 wherein the hygroscopic agent impregnated in the base paper layer comprises any one of the following: lithium chloride, lithium bromide, silica gel, activated alumina, molecular sieves.

4. An exchange element as claimed in any of the preceding claims wherein the base paper is formed from a mixture of said synthetic pulp with a fbirous base material.

5. An exchange element as claimed in claim 4 wherein the fibrous base material comprises any one of the following: asbestos fibre, cellulose fibre, glass fibre, carbon fibre, ceramic fibre.

6. An exchange element as claimed in claim 4 or claim 5 wherein the synthetic pulp comprises 20 to 40% by weight of the base paper.

7. An exchange element as claimed in claim 6 wherein the synthetic pulp comprises 30% by weight of the base.

8. An exchange element as claimed in any of the preceding claims wherein marginal edge portions of the base paper layers are coated with an abrasion resistant substance.

9. An exchange element as claimed in any of the preceding claims wherein the laminate is formed into a drum shape for use in a drum shaped rotor of a heat exchanger.

10. An exchange element as claimed in claim 9 wherein the drum shaped laminate comprises concentric rings of the base paper layers.

11. An exchanger for a heat and/or moisture comprising an drum shaped rotary-housing having an inlet and outlet for moist air to be passed through the housing for drying and a further inlet and outlet for dry air to be passed through the housing for extraction of moisture therefrom and a drum shaped laminate mounted concentrically within the housing to extract moisture from air to be processed and to release the moisture so extracted to the dry air passed through the element.

12. An exchanger for heat and/or moisture comprising a drum shaped housing having an inlet and an outlet for moist air to be passed through the housing for extraction of moisture from the air and a further inlet and outlet for dry air to be passed through the housing for extraction of moisture from the housing and an exchange element as claimed in any of claims 1 to 7 wherein the layers of the laminate extend radially in the housing.