A ROTARY HEAT EXCHANGER USING AMAT WITH ANTIFUNGAL AND DEODORIZING FUNCTION

Technical Field

[1] The present invention relates to a rotary heat exchanger having an electric heat mat, in detail, a rotary heat exchanger having an electric heat mat that has high heat transfer efficiency and antibacterial and deodorant functions by stacking an electric heat seat made of a heat retentive filament and an antibacterial seat made of a filament contained with charcoal powder in the electric heat mat. Background Art

[2] Heat exchangers are one of the devices mainly used in air-conditioning systems. Heat exchangers are used to exchange heat between thermal mediums and they largely fall into a sensible heat exchanger that exchanges only the heat (sensible heat) that the gases in the air have, a latent heat exchanger that exchanges only the heat (latent heat) that the moisture in the air has, and a rotary heat exchanger that exchange both sensible heat and latent heat.

[3] The rotary heat exchangers are used to save energy by recovering and reusing as available heat the waste heat from the air discharged outside when ventilating buildings. They are, as shown in FIG. 1, largely composed of a case forming the outer shape, a circular wheel equipped with an electric heat mat, a motor rotating the wheel, and a blower blowing internal and external air. According to this configuration, as the wheel is rotated by the motor and the external air and the internal air pass through the electric heat mat inside the wheel along separate channels, the heat of the internal air is conducted to the mat and retained therein, and then the heat is transferred to the external air after the wheel rotates at a predetermined angle, such that the external air flows inside with the heat.

[4] The thermal efficiency of the rotary heat exchangers depends on the electric heat mats that are the means for heat transfer of the rotary heat exchangers, that is, the media, and accordingly media for increasing the performance of heat transfer and a typical example is the invention disclosed in Patent Registration No. 157214.

[5] The electric heat mat of the invention disclosed in the above patent is a medium for transferring heat, which employs a strand-typed filament having a diameter of 25 to 150 m. The thick strand type filaments that are almost in a liquid state are randomly jetted from a plurality of nozzles in a matrix shape, as shown in FIGS. 2 and 3, and the matrix-shaped filaments are sequentially stacked from the bottom into a mat shape having about a 5 cm thickness. Thereafter, a thermal plate is attached to the upper and lower sides and slightly pressed such that the weight per unit area (referred to as green density) is about 700g/m ² . In this configuration, since the filaments inside the mat are in contact with each other under high temperature, the contact portions are interrelated by heat. As the electric heat mat is formed in a random matrix shape, air passing through the rotary heat exchanger makes turbulent flow in the electric heat mat, such that the energy recovery efficiency increases.

[6] However, since the invention disclosed in the document employs the filaments having a diameter of 25 to 150 m (substantially filaments having a diameter in the range of 72 to 80 m), unlike common rotary heat exchangers using filaments having diameters around 25 m, the surface area of the filaments which contacts with the air is small and the heat transfer efficiency decreases.

[7] Further, since the diameter of the filaments is large, they are heavy, such that, as shown in FIG. 4, large centrifugal force is generated by the weight of the filaments when the mat rotates with the wheel. Therefore, when the electric heat mat is used for a long period of time, the filaments that have been uniformly stacked become concentrated to the outer side from the rotary shaft by the centrifugal force in accordance with the weight of them, such that the green density becomes high at the outer side of the wheel and low at the portion close to the rotary shaft of the wheel. As a result, the air that is discharged outside or flows inside flows through the portion with low stacking density, thereby reducing energy recovery efficiency.

[8] Further, in this invention, the long continuous single strands of filaments are randomly jet and stacked, there are many spaces between the strands, such that the surface area of the filaments to contact with air reduces, thereby decreasing the energy recovery efficiency.

[9] Moreover, since the thick filaments randomly jet are weakly connected by heat and stacked in a thickness of about 5 cm, even though the thermal plates are attached to the upper and lower sides of the mat and slight pressed, heat is not transferred well to the filaments stacked in the mat, such that the shape is maintained only by the combining force between them connected by high temperature in forming. Therefore, as the mat rotates and centrifugal force is generated, they become disconnected and the mat concentrates to the outer side such that the energy recovery efficiency is further reduced.

[10] On the other hand, rotary heat exchangers have a problem that since low-temperature external air and high-temperature internal air simultaneously flow into the electric heat mat in the rotary heat exchangers, the moisture contained in the high-temperature internal air condenses into water while passing through the mat. Therefore, when the condensed water remains in the mat, it causes germs to easily propagate in the electric heat mat and be carried indoors by the external air.

[11] Further, there is a problem that malodorous substances in the internal air are collected in the mat of the heat exchanger while passing through the mat and then returned indoors by the external air flowing inside from the outside.

[12] Therefore, ventilation of houses has become of increasingly importance due to noxious substances, such as radon, formaldehyde, and carbon dioxide, in addition to requirements of usual ventilation for residential, commercial, and industrial buildings due to worsening atmospheric environment. Accordingly, it is more required to develop rotary heat exchangers that can remove pollutants and malodorous in response to those demands. Disclosure of Invention Technical Problem

[13] The present invention addresses the problems of rotary heat exchangers in the related art and it is an object of the present invention to provide a rotary heat exchanger having an antibacterial and deodorant electric heat mat which makes it possible to increase heat transfer efficiency by maximizing contact area between the mat and the air where heat is exchanged, keep the density even in a long-time use, maximally prevent propagation of germs in the mat, always supply clean air indoors by removing the malodour from the internal air collecting in the electric heat mat or noxious substances flowing inside from the outside, before they are introduced indoors. Technical Solution

[14] According to an aspect of the present invention, there is provided a rotary heat exchanger having an antibacterial and deodorant electric heat mat, in which the electric heat mat is formed by stacking: an electric heat seat made of a heat retentive fiber filament having a diameter of 20 m or less and a length of 3 to 10 cm, and made of polyester or nylon; an antibacterial seat mixed with charcoal powder and made of a fiber filament having a diameter of 20 m or less and a length of 3 to 10 cm.

[15] In the rotary heat exchanger, the electric heat seat and the antibacterial seat have a thickness about 10 mm.

[16] Compression ratio of the electric heat seat is 570 to 630 g/m ² and compression ratio of the antibacterial seat is 3% larger than the compression ratio of the electric heat seat.

[17] The antibacterial seat is disposed at the front and rear ends and a plurality of electric heat seats is disposed inside the antibacterial seats in the electric heat mat.

Advantageous Effects

[18] The present invention has an advantage of maximizing the contact area between the mat and the air by forming a thin electric heat mat, using short filaments having 3 to 10 cm and a diameter of 20 m, and stacking them.

[19] Further, the present invention has an advantage of keeping the performance of heat transfer for a long period of time, because the filaments in the mat do not concentrate to one side even in a long-time use of the mat by forming the electric heat mat, using short filaments having a length of 3 to 10 cm.

[20] Further, the present invention has an advantage of always supplying clean air indoors by collecting and removing germs and malodour in the air with the antibacterial seat mixed with charcoal powder in the mat to purify the air. Brief Description of Drawings

[21] FIG. 1 is a perspective view showing a rotary heat exchanger of the related art.

[22] FIG. 2 is a perspective view illustrating a method of manufacturing an electric heat mat of the related art.

[23] FIG. 3 is a cross-sectional view showing an electric heat mat of the related art.

[24] FIG. 4 is a cross-sectional view showing a use of an electric heat mat of the related art.

[25] FIG. 5 is an exploded perspective view showing a rotary heat exchanger according to an embodiment of the present invention.

[26] FIG. 6 is a view illustrating air flow in the assembled configuration shown in FIG. 5.

[27] FIG. 7 is a graph showing energy recovery efficiency and air flow velocity to mat density of an electric heat mat according to an embodiment of the present invention.

[28] FIG. 8 is a graph showing system efficiency of a heat exchanger to mat density of an electric heat mat according to an embodiment of the present invention.

[29] FIG. 9 is a graph showing deodorization efficiency to time of an antibacterial seat according to an embodiment of the present invention. Best Mode for Carrying out the Invention

[30] Preferred embodiment of an antibacterial and deodorant mat for a rotary heat exchanger according to an embodiment of the present invention and the configuration of a rotary heat exchanger using the mat are described hereafter in detail with the accompanying drawings.

[31] FIG. 5 is an exploded perspective view of an antibacterial and deodorant mat for a rotary heat exchanger according to an embodiment of the present invention and a rotary heat exchanger using the mat and FIG. 6 is a perspective view showing flow of external air and internal air in the assembly shown in FIG. 5.

[32] As shown in FIG. 5, a rotary heat exchanger according to an embodiment of the present invention includes a circular wheel 7 having a motor shaft hole 9 at the center and a frame to accommodate an electric heat mat 1, the electric heat mat 1 accommodated in the circular wheel 7, and a motor 11 having a shaft 13 fitted in the motor shaft hole 9 of the wheel 7.

[33] According to the rotary heat exchanger having the above structure, as shown in FIG.

6, as the wheel 7 is rotated by the motor 11, the electric heat mat 1 inside the wheel 7 takes the sensible heat and the latent heat from air discharged from indoors to the outside and then transfers the sensible heat and latent heat to air newly flowing inside from the outside.

[34] The electric heat mat 1 is a medium allowing heat transfer between internal air discharged outside and external air introduced for ventilation. The electric heat mat 1 of an embodiment of the present invention is composed of electric heat seats 3 made of a heat retentive fiber and antibacterial seats 5 made of a fiber contained with charcoal.

[35] The electric heat mat 1 according to an embodiment of the present invention has some structural features to improve energy recovery efficiency and keep the structure, in which the structural features are making the diameter of a filament small, making the seats thin, and appropriately arranging the bacterial seats and the electric heat seats.

[36] The electric heat seat 3 is manufactured by cutting a heat retentive fiber filament of

10 to 20 m diameter in 3 to 10 cm, and press-forming it while heating.

[37] The electric heat seat 3 is a medium for heat transfer and it is advantageous to use fiber having large heat capacity for the electric heat seat 3 to take/discharge heat from/ to internal air and then effectively heat/cool external air. For this purpose, an embodiment of the present invention uses polyester or nylon that has high heat recovery rate from discharged air, is inexpensive and not corroded by internal air for the electric heat seat 3 on account of large heat capacity.

[38] Using a filament having a diameter over 20 m to manufacture the electric heat seat reduces the surface area of the filament which contacts with the air, such that it reduces performance of retaining and transferring heat. Therefore, an embodiment of the present invention uses a fiber filament having a diameter of 20 m or less for the electric heat seat to preclude the problem.

[39] In this configuration, the contact area with the air and the thermal efficiency are maximized by forming the electric heat seat to have a thickness of about 10 mm, using not long strand-type filaments commonly used, but filaments having a small length of 3 to 10 cm.

[40] That is, using a filament grey yarn having a length of 3 cm or less significantly increases air resistance when the air passes through the mat because the density is considerably high after the mat is formed, whereas using a filament grey yarn having a length of 10 cm or more makes it difficult to absorb heat sufficiently from the internal air.

[41] Further, making the length of the filament grey yarns used for the electric heat seat 3 to 10 cm, as described above, makes it possible to form uniformly the electric heat seat, because the filaments are short.

[42] That is, when a fabric having a thickness of about 10 mm is formed by short filament grey yarns having a length of 3 to 10 cm, since the thickness is about 10 mm, short filaments of about 3 to 4 cm are disposed once only in the up-down direction or covered in between long filaments, such that it is possible to reduce porosity as compared with when only long strands are used or only filament having a predetermined length are used. Further, it is possible to make density uniform as compared with long grey yarns, such that heat transfer efficiency increases and the wheel can smoothly rotate without vibration due to the centrifugal force when the mat disposed inside the wheel is rotated with the wheel, because the weight of the mat is uniformly distributed (the weight does not concentrate on one side).

[43] Further, in this embodiment, unlike common electric heat seat of the related art which have a thickness of about 5 to 7 cm, the thickness of the electric heat seat is around 1 cm, on account of the problems with electric heat seats in the related art and features of the filament of the present invention.

[44] That is, electric heat seats used in rotary heat exchangers of the related art are formed by randomly jetting strands in an almost thick liquid state having a diameter around 30 m with a plurality of nozzles to be stacked from the bottom in a mat having about a 5 cm thickness and then pressing thermal plates to the top side and bottom side of the mat, as shown in FIGS. 2 and 3. In this structure, the filaments in the mat are still at high temperature, such that they bond at contact portions by heat and the green density of the electric heat mat after the forming is about 700 g/m ² .

[45] Since electric heat mats of the related art are formed by thick filaments in the method described above, combining force between the filaments in the mat decreases in a longtime use as described above, such that the filaments that have been uniformly stacked in the mat concentrate to the outer side of the wheel from the rotary shaft by centrifugal force generated by rotation of the wheel as shown in FIG. 4. Therefore, the stacking density of the filament is high at the outer side of the wheel and low at the inner side of the wheel. Accordingly, air, which is discharged outside or flows inside, flows to the portion where the stacking density is low, thereby significantly reducing heat transfer efficiency.

[46] When a heat exchanger employs the electric heat seat described above, efficiency of the heat exchanger usually depends on the thickness of the mat, compression ratio, rotation speed of the heat exchanger, and air flow rate. However, the entire thickness of the mat should be limited to 5 to 10 cm because the mat is used in a limited space, and the rotation speed of the heat exchanger is limited to 25 to 30 rpm in consideration of heat transfer efficiency. Therefore, the applicant(s) set the thickness of the mat and the rotation speed of the heat exchanger within the limited ranges and measured the heat transfer efficiency and the air flow rate to the compression ratio of the filaments of the electric heat seat, and the result was shown in FIG. 7. It can be seen from FIG. 7 that as the compression ratio of the electric heat seat increases, the heat transfer ef- ficiency increases, whereas the air flow rate decreases. The system efficiency of the heat exchanger is represented by the system efficiency curve shown in FIG. 8. It can be seen from FIG. 8 that the system efficiency is optimal at 570 to 630 g/m ² which is 5% from 600 g/m ² compression ratio of the electric heat seat.

[47] Therefore, in the present invention, in order to overcome the problems with rotary heat exchangers of the related art, the diameter is 20 m or less, which is less than the related art, the length of filaments is small, 3 to 10 cm, which is not a strand type, the thickness of the electric heat seat is 10 mm which is less than the related art, and the compression ratio of the electric heat seat is within 570 to 630 g/m ² which is also less than the related art.

[48] Meanwhile, the rotary heat exchanger, as shown in FIG. 1, absorbs cold heat from cold water discharged from the indoor in summer and warmth from hot air discharged from the indoor in winter. Therefore, heat is discharged from the moisture contained in high-temperature and high-humidity external air in summer and the moisture contained in the high-temperature and high-humidity internal air in winter by heat transfer while the moisture passes through the electric heat mat, such that the moisture is condensed into water. When remaining in the electric heat mat, the condensed water allows germs to propagate or the internal pollutants can adhere. Accordingly, the germs and pollutants may be carried again indoors by external air that is introduced inside.

[49] Accordingly, the present invention is provided with an antibacterial and deodorant seat (hereafter, referred to as antibacterial seat) having antibacterial and deodorant functions to prevent the germs and pollutants remaining in the electric heat seat from being carried indoors by external air. The antibacterial seat 5 is formed by collecting and pressing fiber filaments contained with porous charcoal powder and forms the electric heat mat by being stacked with the electric heat seat inside the wheel.

[50] The antibacterial seat 5 of the present invention is formed by producing grey yarns having a 10 to 20 m diameter by mixing 1 to 15% charcoal powder of which the particles' size is 0.7 to 2 m with a polymer raw material, cutting them into 3 to 10 cm the same as the electric heat seat, and then making them have a 10 mm thickness. However, the compression ratio of the antibacterial seat is set about 3% larger than the compression ratio of the electric heat seat described below.

[51] The porous charcoal used for the antibacterial seat 5 has a specific surface area of

300 to 1000 m ² /g and the charcoal powder is mixed in the grey yarns, such that the porosity is increased by the charcoal powder itself or the charcoal powder in the powder mixture. Accordingly, air permeability of the antibacterial seat 5 increases, and moisture and germs in the air are effectively absorbed and removed by a plurality of fine holes in the charcoal, such that deodorization, purification, and dehumidification are performed. [52] However, when the charcoal powder is contained in the grey yarns of the antibacterial seat 5, the performance of heat transfer reduces by 0.5 to 7.5%, as compared with pure fiber when other kinds of powder, such as the charcoal powder, are not contained, such that the heat recovery function is deteriorated.

[53] Addressing the problem described above, the present invention removes the problem, as described below, by increasing the contact area with air by increasing the manufacturing density of the antibacterial seat 5, and stacking the antibacterial seat 5 and the electric heat seat 3. That is, it is possible to increase again the performance of heat transfer reduced by the charcoal powder contained in the grey yarns by increasing the compression ratio when manufacturing fabric from the grey yarns mixed with charcoal and a polymer raw material.

[54] Therefore, in the present invention, it could be seen from a test that it is possible to achieve the same performance of heat transfer in the antibacterial seat as the electric heat seat by increasing the compression ratio of the antibacterial seat by about 3% than the compression ratio of the electric heat seat.

[55] The object of the antibacterial seat of the present invention is not to remove germs or stink in the air existing in a space to ventilate, but to remove malodour and germs generated by condensed water remaining in the electric heat mat, such that the antibacterial seat should have deodorant and antibacterial functions.

[56] FIG. 9 is a graph showing a test result regarding the deodorization efficiency of the antibacterial seat of the invention conducted by FITI Testing & Research Institute. According to this graph, the deodorization efficiency was about 56% after 30 minutes passed, but the deodorization efficiency gradually increased as time passed, the deodorization efficiency reached about 60% after 120 minutes passed, which shows that the deodorization efficiency increased by 3 to 4% over 90 minutes. It can be seen from the above that the antibacterial seat has an antibacterial function itself. Further, considering the durability of the electric heat seat is over 3 years, there is little probability for malodour to remain in the electric heat mat as time passes.

[57] Further, FITI Testing & Research Institute has conducted a test for antibacterial function under conditions shown in Table 1 to examine the antibacterial function of the antibacterial seat of the present invention. It can bee seen from the test that the reduction ratio of germs (bacteria) is very high, at 98.3% and 99% and this antibacterial function is because the charcoal powder is contained in the antibacterial seat of the present invention, considering the antibacterial function of common electric heat seats is around 50%.

[58] Table 1 [Table 1]

[Table ]

Test result of antibacterial function of antibacterial seat

[59]

[60] Test Condition

[61] 1. Test Bacteria

[62] Test Bacteria - Staphylococcus aureus ATCC 6538

[63] Test Bacteria - Klebsiella pneumoniae ATCC 4352

[64] 2. Cone of Inoculm

[65] Test Bacteria 13 10 ⁴ CFL/mL

[66] Test Bacteria 13 10 ⁴ CFL/mL

[67] 3. Control specimen: Cotton standard fabric (Ks K0905: 2001)

[68] 4. Nonionic surfactant: Tween 80, added to Inoculm (0.05%)

[69] As described above, the performance of heat transfer is reduced by the charcoal powder contained in the antibacterial seat, such that the heat recovery performance for recovering heat from discharged air reduces. However, in the present invention, the problem is removed by appropriately adjusting arrangement of the antibacterial seat and the electric heat seat and the compression ratio of them.

[70] First, the electric heat seat and the antibacterial seat of the present invention have a thickness of about 10 mm and they are arranged in consideration of the heat transfer efficiency and the antibacterial and deodorant function, in which it is preferable that they are stacked respectively at a thickness of 10 mm and the total thickness of the electric heat mat is 35 to 80 mm to prevent excessive resistance against air flow.

[71] As described above, it is preferable to arrange the antibacterial seat 5 at the front and the rear and the electric heat seat 3 between the antibacterial seats 5 as shown in FIG. 5, this is because it is possible to supply more pure air indoors by making air, which passes through the electric heat mat, flow through the deodorant and antibacterial seat.

[72] The electric heat seat of the present invention is small in weight per unit area, but large in actual heat transfer efficiency as compared with those in the related art. Further, the antibacterial seat has the same heat transfer efficiency as the electric heat seat by increasing the compression ratio over that of the electric heat seat, such that the heat transfer efficiency is not smaller relatively to rotary heat exchangers of the related art irrespective of the types of arrangement of the electric heat seat and the an- tibacterial seat. [73] Therefore, as the basic principle of arranging the seats of the present invention, they are arranged first in consideration of the antibacterial and deodorant functions, other than the heat transfer efficiency. [74] Since it is preferable to dispose the rotary heat exchanger such that germs and condensed water in the electric heat seat cannot be carried indoors by air, it is preferable to arrange the antibacterial seat at the front and the electric heat seat at the rear. [75] Further, it is more preferable to dispose the antibacterial seat at the front through which external air flows inside to prevent germs and moisture from being carried inside with external air introduced from the outside. [76] Further, the electric heat seat and the antibacterial seat are commonly formed in a fan shape such that a rotary shaft can be inserted in the center and they can be fitted on the shaft, and then they are assembled. According to the test result, the less the number of pieces, the more the heat transfer efficiency increases, whereas the more the structural rigidity decreases. Further, four pieces satisfy both of the structure rigidity and heat transfer efficiency.