Description

HEAT EXCHANGER

Technical Field

[1] This invention relates to air ventilation systems, specifically to heat exchangers used in these ventilation systems. Background Art

[2] Several types of heat exchangers are installed in ventilation systems. Most often counter flow and cross flow heat exchangers are used, in which outgoing indoor air heats up the incoming outside air. Heat exchangers are particularly important during the cold season, when heat and moisture is exhausted from ventilated rooms together with outgoing indoor air and cold and dry air is supplied to the rooms form outside.

[3] Usually arrangements of aluminum foil are used for manufacturing the mentioned heat exchangers. Aluminum is a good heat conductor, but it is totally impermeable to moisture. Sometimes heat- and moisture-permeable paper is used in heat exchangers. Heat exchangers made of such paper effectively transfer heat and moisture from warm and humid air to cold and dry air. The main deficiency of paper heat exchangers is that the heat exchangers change their form as the paper becomes moist - exchangers warp, transient reversible expansion of the moist paper also takes place. This property of paper heat exchangers limits their usability in humid rooms. Important to note that aluminum foil is unsuitable for formation of corrugated layers for counter flow heat exchangers, because aluminum foil easily tears in fold joints during formation of folds in essentially three directions.

[4] American patent No US7188666, published on March 13 2007, describes a cross flow heat exchanger for ventilation systems. This heat exchanger is made essentially of corrugated paper layers and paper dividers. A spongy paper is used for inducing capillarity and improvement of moisture transfer.

[5] European patent No EP1249669, published on October 16 2002, describes the element of a ventilation system accommodating a heat exchanger. Provision is made for manufacturing the heat exchanger elements from plastic, thus forming enclosed air conduits. A type of plastic to be used should facilitate effective heat transfer.

[6] American patent No US2001032714, published on October 25 2001, describes an element of ventilation system, the main purpose thereof being heat transfer from used air and fresh intake air while totally preventing mixing of these air flows. The air conduits used for this purpose are made of plastic.

[7] International patent application WO8607133, published on December 4 1986, solves manufacturing problems of heat exchangers by employing ultrasound or radio welding of plastic corrugated layers.

[8] All mentioned inventions are based on utilization of different materials in manufacturing of heat exchangers thereby solving facilitation problems of heat and moisture transfer from used air to fresh intake air. However, neither invention offers a universal solution ensuring effective heat and moisture transfer in a heat exchanger of a ventilation system for reduction of loss of the both components. It is particularly important in workspaces and residential premises. Heat exchangers themselves should not deform under influence of humidity. Manufacturing of a heat exchanger meeting all three criteria is possible only when materials are selected and arranged correctly. Additionally, it is important that composition of selected materials would allow formation of both counter and cross flow heat exchangers. Disclosure of Invention Technical Problem

[9] This invention seeks to create a counter flow heat exchanger for ventilation systems.

The heat exchanger should effectively facilitate heat and moisture transfer while suffering relatively small deformations under influence of these two factors. Technical Solution

[10] Based on these criteria, a counter flow heat exchanger has been developed, in which corrugated layers a made of thermoplastic and dividers between the layers are made of moisture- and heat-permeable paper. Use of plastic for manufacturing of corrugated layers allows formation of additional bumps equalizing air flow across the whole cross-section. Description of Drawings

[11] Fig. 1 - counter flow heat exchanger (perspective projection);

[12] Fig. 2 - isometric projection of counter flow heat exchanger (state of assembly);

[13] Fig. 3 - a fragment of counter flow heat exchanger (frontal projection);

[14] Fig. 4 - a composite element of counter flow heat exchanger.

Mode for Invention

[15] The preferred embodiment of this invention is a counter flow heat exchanger, made of layers (3) illustrated in Fig. 4. Each layer (3) is made of paper separator (1) and corrugated plastic separator (2) of essentially same planar dimensions. These separators are joined together by gluing, welding or otherwise and compose one layer of the heat exchanger. These layers are mounted on each other rotating each consecutive layer by 180° around axis Z relative to the previous one. Thus an arrangement showed in Fig. 3 is formed. In every other layer of this arrangement air flows in one direction, in the remaining layers, in the reverse direction.

[16] In one version of embodiment air from inside of the building enters into the heat exchanger through side (G-H) and leaves it through side (C-D). Outside air enters into

the heat exchanger through side (G-F) and leaves it through side (D-E). In sections (G-H-F) and (C-D-E) used and fresh air flows in approximately perpendicular directions, while in section (H-C-E-F) the air flows in counter directions. It is in this section that the most effective heat and moisture transfer takes place; therefore the length of the section determines efficiency of the heat exchanger. At the sides of the exchanger air paths lengths differ in this embodiment version, i.e. outside air travels much shorter distance along the path (F-E) than along the path (G-H-C-D), therefore the air traveling along the path (F-E) doesn't have time to absorb and accumulate as much heat and moisture as the air traveling along the path (G-H-C-D). For this reason another version of embodiment is possible, where corrugated layers in the section indicated by dash-dot line (4) are formed with additional bumps or barriers slowing down the air flow and equalizing air flow across all cross-section of the heat exchanger.