Heat exchanger, heat recovery ventilator including the same, and method for defrosting and checking operations thereof

Abstract

The present invention relates to a heat exchanger, a method for manufacturing the same, a heat recovery ventilator (HRV) including the same, and a method for defrosting and checking operations thereof.

Claims

1. A heat exchanger comprising: a plurality of stacked heat exchange elements; support plates attached to the top and bottom surfaces of said stacked heat exchange elements; and connection members attached to the respective corners of said stacked heat exchange elements, wherein each of said heat exchange elements comprises: a heat exchange surface spacer member having a plurality of first flow paths arranged in parallel to each other; and a pair of heat exchange element spacer members attached to the upper surface of the heat exchange surface spacer member so as to be spaced apart from each other, a second flow path is formed between the pair of heat exchange element spacer members along a direction perpendicular to the first flow paths, wherein the plurality of heat exchange elements are formed of corrugated cardboard, and the plurality of first flow paths are formed by the corrugations of the corrugated cardboard, wherein each of heat exchange element spacer members is formed by closing both ends of the corrugated cardboard and bending both ends of the corrugated cardboard along cutting lines spaced from the respective closed ends and positioned perpendicular to the flow direction of the plurality of first flow paths.

2. The heat exchanger according to claim 1, wherein said heat exchanger further comprises: a partition wall installed on one outside of said plurality of heat exchange elements in a direction perpendicular to the direction where said plurality of heat exchange elements are stacked, at one end of the flow direction of said plurality of first flow paths; and an intermediate chamber which is installed on another exterior side of said plurality of heat exchange elements so as to face said partition wall and through which said plurality of first flow paths communicate.

Description

DESCRIPTION OF DRAWINGS

(1) FIG. 1 schematically illustrates a general heat recovery ventilator.

(2) FIGS. 2, 3 and 4 schematically illustrate conventional heat exchangers.

(3) FIGS. 2 and 4 illustrate multi-flow-path heat exchangers.

(4) FIG. 3 illustrates a single-flow-path heat exchanger.

(5) FIG. 5 is a plan view for explaining the shape of ice formed in the heat exchanger.

(6) FIGS. 6, 7 and 8 schematically illustrate a defrosting operation of the conventional heat recovery ventilator.

(7) FIGS. 9A-9D and 10 illustrate a process for manufacturing a heat exchange element used in a heat exchanger according to a first embodiment of the present invention and the heat exchanger manufactured through the manufactured process.

(8) FIGS. 11A-11B and 12 illustrate a process for manufacturing a heat exchange element used in a heat exchanger according to a second embodiment of the present invention and the heat exchanger manufactured through the manufactured process.

(9) FIG. 12 illustrates the heat exchanger manufactured through stacking the heat exchange elements of FIGS. 11A-11B.

(10) FIG. 13 schematically illustrates a double heat exchanger according to a third embodiment of the present invention, including a partition wall and an intermediate chamber formed therein.

(11) FIG. 14 illustrates a heat exchanger for explaining a method for defrosting operation according to a first embodiment of the present invention, including a flow path selection damper and a connection path for connecting an outdoor air introduction chamber and a supplied air discharge chamber.

(12) FIG. 15 illustrates an example in which the defrosting operation of FIG. 14 is applied to the double heat exchanger of FIG. 13.

(13) FIG. 16 illustrates a heat exchanger for explaining a method for defrosting operation according to a first embodiment of the present invention, including another flow path selection damper and another connection path for connecting the interior and the exterior.

(14) FIG. 17 illustrates an example in which the defrosting operation of FIG. 16 is applied to the double heat exchanger of FIG. 13.

(15) FIGS. 18, 19 and 20 are flowcharts illustrating three embodiments of a method for defrosting operation, normal operation, and checking operation of a heat recovery ventilator.

(16) FIG. 18 illustrates a method in which three temperature sensors are used.

(17) FIG. 19 illustrates a method in which two hole sensors are used.

(18) FIG. 20 illustrates a method in which three temperature sensors and two hole sensors are used.

BEST MODE FOR THE INVENTION

(19) Descriptions for Heat Exchanger Including Both of Multi-Flow-Path Structure and Single-Flow-Path Structure

(20) Referring to FIGS. 9A-9D and 10, a heat exchanger according to a first embodiment of the present invention will be described. Referring to FIGS. 11A-11B and 12, a heat exchanger according to a second embodiment of the present invention will be described. Furthermore, a double heat exchanger according to a third embodiment of the present invention, to which the first and second embodiments may be applied, will be described with reference to FIG. 13.

(21) In order to solve problems of a heat exchanger, an exhaust air flow path of a heat exchange element must have a single-flow-path structure, and spacer protrusions which disturb an air flow and on which foreign matters such as dust are accumulated must be removed.

(22) The embodiments of the present invention provide a heat exchanger which includes both of a single-flow-path structure and a multi-flow-path structure, in order to satisfy such a condition.

(23) FIGS. 9A-9D illustrate a process for manufacturing a heat exchange element using a plastic corrugated cardboard according to an embodiment of the present invention. FIG. 10 illustrates a multi/single-flow-path heat exchanger manufactured through the process of FIGS. 9A-9D.

(24) FIG. 9A illustrates a plastic corrugated cardboard which has a multi-flow-path formed through extrusion molding. Referring to FIG. 9B, both ends of the multi-flow-path in the plastic corrugated cardboard illustrated in FIG. 9A are completely sealed through thermal bonding, and the plastic corrugated cardboard is cut along a cutting line 76 which is formed on the bottom surface thereof at a predetermined distance from either thermal bonding line 78, in a direction perpendicular to the multi-flow-path. The predetermined distance corresponds to ½ of the thickness of the corrugated cardboard. Referring to FIG. 9C, both ends of the plastic corrugated cardboard, which are sealed through thermal bonding, are bent by 90 degrees along the cutting line 76. Referring to FIG. 9D, both ends of the plastic corrugated cardboard are bent by 180 degrees so as to form spacer members 73 of the heat exchange element. Thus, the heat exchange element 71 includes two heat exchange surfaces 1, a heat exchange surface spacer member 72, and the heat exchange element spacer members 73.

(25) The thermal bonding is one of processes for closing both ends, and another closing process may be applied.

(26) FIG. 10 illustrates a heat exchanger 70 including a plurality of heat exchange elements 71, two insulation support plates 74, and fourth connection members 75, which form a multi-flow-path structure and a single-flow-path structure. The plurality of heat exchange elements 71 are manufactured through the process described with reference to FIGS. 9A-9D and then stacked. The multi-flow-path structure formed through the heat exchange surface spacer members 72 is used as a flow path for supplied air stream 22-23, and the single-flow-path structure formed through the heat exchanger spacer members 73 is used as a flow path for exhaust air stream 32-33. In this case, the use of the two flow paths may be changed in a place where foreign matters such as ice or dust are not accumulated.

(27) In the heat exchanger of FIG. 10, the heat exchanger spacer member 73 for forming the single-flow-path structure is formed by thermally bonding and bending a plastic corrugated cardboard. In a heat exchanger of FIG. 12, however, a heat exchange element spacer member 83 is formed using another material such as foamed plastic. FIGS. 11A-11B illustrate a process for manufacturing a heat exchange element of the heat exchanger of FIG. 12.

(28) Referring to FIGS. 11A-11B, the heat exchange element spacer member 83 is attached at both ends of a plastic corrugated cardboard 87, thereby forming a heat exchange element 81 which includes two heat exchange surfaces 1, a heat exchange surface spacer member 82, and the heat exchange element spacer member 83.

(29) FIG. 12 illustrates the heat exchanger 80 including a plurality of heat exchange elements, two insulation support plates 84, and four connection members 85, which form a multi-flow-path structure and a single-flow-path structure. The plurality of heat exchange elements are manufactured through the process described with reference to FIGS. 11A-11B, and then stacked. The multi-flow-path structure formed through the heat exchange surface spacer members 82 is used as a flow path for supplied air stream 22-23, and the single-flow-path structure formed through the heat exchange element spacer members 83 is used as a flow path for exhaust air stream 32-33. In this case, the use of the two flow paths may be changed in a place where foreign matters such as ice or dust are not accumulated.

(30) The heat exchangers of FIGS. 10 and 12 include the single-flow-path structure serving as the flow path for the exhaust air stream, and have no spacer protrusions formed in the flow path. Thus, the heat exchangers may compensate the defects of the multi-flow-path heat exchanger 40 or 60 vulnerable to ice formation or the single-flow-path heat exchanger 50 vulnerable to dust. Furthermore, low-priced extrusion-molded plastic corrugated cardboards may be used to simply manufacture the heat exchangers 70 and 80 without applying an adhesive on the heat exchange surfaces 1.

(31) The heat exchangers 70 and 80 according to the embodiment of the present invention have considerably compensated the defects of the existing heat exchangers 40, 50, and 60, but the outdoor air temperature at which ice formation begins to occur is equal to that of the existing heat exchangers 40, 50, and 60. FIG. 13 illustrates a double heat exchanger 90 which includes a partition wall 98 and a supplied-air-stream intermediate chamber 99 which are additionally installed in the heat exchanger 70 or 80 according to the embodiment of the present invention. The partition wall 98 is installed on one surface of a multi-flow-path structure, and the supplied-air-stream intermediate chamber 99 is installed on the other surface of the multi-flow-path structure. Outdoor air 22 receives energy from exhaust air stream through heat exchange surfaces 1 while passing through the multi-flow-path structure formed through heat exchange surface spacer members 92, and then becomes supplied air stream. The supplied air stream is introduced into the supplied-air-stream intermediate chamber 99, and receives energy from the exhaust air stream through the heat exchange surfaces while passing through the multi-flow-path structure. Then, the supplied air stream becomes supplied air 23 to be supplied to the interior. Return air 32 transmits energy to the supplied air stream through the heat exchange surfaces 1 while passing through a single-flow-path structure formed through heat exchanger spacer members 93, and becomes exhaust air to be discharged to the exterior. Two heat exchange element support plates 94 and four connection members 95 serve to fix the stacked heat exchange elements 91, and the partition wall 98 serves to prevent the mixing of the outdoor air 22 and the supplied air 23.

(32) Table 3 comparatively shows ice formation areas of the multi-flow-path heat exchanger 40 or 60 and the double heat exchanger 90 having the same heat exchange efficiency as the high-efficiency heat exchangers 40, 50, and 60 shown in Table 1, depending on outdoor temperatures. The return air has a temperature of 26° C. and a relative humidity of 60%.

(33) TABLE-US-00003 TABLE 3 Multi-flow-path heat exchanger Double heat exchanger Outdoor Ice Ice Available Ice Ice Available air formation formation heat formation formation heat temperature area width exchange area width exchange (° C.) (%) (%) area (%) (%) area −2 0.0 0.0 100.0 0.0 0.0 100.0 −4 0.2 3.0 97.0 0.0 0.0 100.0 −6 1.8 10.0 90.0 0.0 0.0 100.0 −8 3.5 15.5 84.5 0.0 0.0 100.0 −10 7.0 22.5 77.5 0.3 7.0 99.7 −12 9.9 28.0 72.0 1.7 17.5 98.3

(34) In the double heat exchanger 90 according to the embodiment of the preset invention, the outdoor air temperature at which ice formation occurs is lower by 5 to 6° C. than in the multi-flow-path heat exchanger 40 or 60 and the single-flow-path heat exchanger 50. Furthermore, the available heat exchange area ratio is determined by the ice formation area ratio instead of the ice formation width ratio, like the single-flow-path heat exchanger.

(35) Descriptions for Defrosting Operation of Heat Recovery Ventilator

(36) Referring to FIGS. 14 and 15, a defrosting operation according to a first embodiment of the present invention will be described. Referring to FIGS. 16 and 17, a defrosting operation according to a second embodiment of the present invention will be described.

(37) The embodiments of the present invention provide a new method for a defrosting operation for removing ice formation which occurs in a flow path for exhaust air stream of a heat exchanger or blockage of a flow path for supplied air stream, which is caused by snow.

(38) FIG. 14 illustrates an example in which a flow path selection damp 104 (first flow path selection damper) and a connection path (first connection path) for connecting an exhaust air inlet (that is, outdoor air introduction chamber) and a supplied air outlet (that is, supplied air discharge chamber) are installed. When a defrosting operation is required to remove ice formed in a flow path for exhaust air stream or blockage of a flow path for supplied air stream, caused by snow, in the heat exchanger, the flow path selection damper 104 blocks the introduction of outdoor air, and connects the supplied air outlet and the outdoor air inlet. In the flow path for the exhaust air stream, return air 32 is passed through the return air introduction chamber and the heat exchanger 40, 50, or 80, and then discharged as exhaust air 33 to the exterior. In the flow path for the supplied air stream, internal air 25 is circulated through the supplied air discharge chamber, the connection member, the outdoor air introduction chamber, and the supplied air flow path of the heat exchanger 40, 50, or 80. In a section corresponding to the ice formation area, the temperature of the circulated air 25 decreases while the circulated air 25 melts ice formed in the exhaust air flow path through the heat exchange surface. In a section where heat exchange may be performed, the temperature of the circulated air 25 increases while the circulate air 25 receives energy from the exhaust air stream. The exhaust air stream 32-33 supplies energy to the circulated air and partially contributes to the frosting operation, while passing through the exhaust air flow path of the heat exchanger. Then, the exhaust air stream 32-33 is discharged as exhaust air to the exterior. The blockage caused by snow in the outdoor air introduction part of the heat exchanger may be removed through the same method.

(39) The heat exchanger used at this time may include the multi-flow-path heat exchangers 40 and 60, the single-flow-path heat exchanger 50, and the multi/single-flow-path heat exchanger illustrated in FIGS. 9A-9D, 10, 11A-11B, 12 and 13.

(40) FIG. 15 illustrates a heat recovery ventilator which performs a defrosting operation using the double heat exchanger 90 according to the third embodiment of the present invention (refer to FIG. 13). The heat recovery ventilator performs a defrosting operation in the same method as illustrated in FIG. 14.

(41) The defrosting method of FIGS. 14 and 15 is a negative pressure-type defrosting method which does not supply outdoor air to the interior but discharge outdoor air to the exterior during a defrosting operation. Thus, although the ventilation efficiency is not degraded like the method of FIG. 6, a problem may occur when the defrosting method is used in a place where outdoor air is introduced into the interior through a contaminated path such as an outlet of a kitchen hood.

(42) FIG. 16 illustrates that a connection path (second connection path) for connecting the exhaust air outlet (that is, exhaust air discharge chamber) to the interior is installed and a flow path selection damper 105 (second flow path selection damper) are installed in order to compensate the problem of the defrosting method illustrated in FIG. 14. The defrosting operation of FIG. 16 is different from that of FIG. 14 in that exhaust air is not discharged to the exterior but reintroduced to the interior by the flow path selection damper 105. That is, the return air 132 becomes reintroduced air 133 which is reintroduced to the interior through the return air introduction chamber, the heat exchanger exhaust air flow path, and the exhaust air discharge chamber. The circulated air 25 melts ice while internally circulated in the same method as illustrated in FIG. 14. In this method, ventilation is stopped during the defrosting operation. Thus, this method may be effectively used in a place where ventilation efficiency does not matter.

(43) The heat exchanger used at this time may include the multi-flow-path heat exchangers 40 and 60, the single-flow-path heat exchanger 50, and the multi/single-flow-path heat exchanger illustrated in FIGS. 9A-9D, 10, 11A-11B, 12 and 13.

(44) FIG. 17 illustrates a heat recovery ventilator which performs a defrosting operation in the same manner as illustrated in FIG. 16, using the double heat exchanger 90 according to the third embodiment of the present invention (refer to FIG. 13).

(45) Method for Defrosting Operation, Normal Operation, and Checking Operation

(46) Referring to FIGS. 18 to 20, three embodiments of a method for a defrosting operation, a normal operation, and a checking operation will be described.

(47) The embodiments of the present invention provide a method in which a heat recovery ventilator detects flow path blockage when the flow paths for supplied air stream and exhaust air stream are clogged with dust or ice, issues an alarm, and performs a defrosting operation and a normal operation.

(48) When the flow path for supplied air stream or exhaust air stream in the heat exchanger is clogged with ice or dust, the resistance of the air stream is increased to reduce the amount of air passing through the corresponding flow path, and an available heat exchange area is reduced. Table 4 shows the influence of flow path blockage on temperature exchange efficiency, heat exchange efficiency, and ventilation efficiency.

(49) TABLE-US-00004 TABLE 4 Flow path blockage Temperature Heat Supplied Exhaust exchange exchange Ventilation Flow path resistance air air efficiency efficiency efficiency Supply Exhaust 1 normal blocked decrease decrease normal normal increase 2 blocked normal increase decrease slight increase normal decrease 3 blocked normal unknown decrease decrease increase increase

(50) Here, the heat exchange efficiency ε may be expressed through the density ρ.sub.OA, of outdoor air, the air amount Q.sub.OA, the density ρ.sub.RA of return air, the return air temperature T.sub.RA, the supplied air temperature T.sub.SA, and the outdoor air temperature T.sub.OA, and the temperature exchange efficiency η may be simply expressed through the return air temperature T.sub.RA, the supplied air temperature T.sub.SA, and the outdoor air temperature T.sub.OA, without the supplied air amount and the exhaust air amount.

(51) $\begin{array}{cc}\epsilon =\frac{{\rho }_{\mathrm{OA}}{Q}_{\mathrm{OA}}\left(T_{\mathrm{SA}}-T_{\mathrm{OA}}\right)}{C_{\mathrm{MAX}}\left(T_{\mathrm{RA}}-T_{\mathrm{OA}}\right)},C_{\mathrm{MAX}}=\mathrm{Max}\left({\rho }_{\mathrm{OA}}{Q}_{\mathrm{OA}},{\rho }_{\mathrm{RA}}{Q}_{\mathrm{RA}}\right)& \mathrm{Equation}1\\ \eta =\frac{T_{\mathrm{SA}}-T_{\mathrm{OA}}}{T_{\mathrm{RA}}-T_{\mathrm{OA}}}& \mathrm{Equation}2\end{array}$

(52) As shown in Table 4, when the flow path for the supplied air stream or exhaust air stream is blocked, the heat exchange efficiency decreases in all cases, but the temperature exchange efficiency differs depending on cases.

(53) In the method according to the first embodiment of the present invention, three temperature sensors are used to perform a defrosting operation, a normal operation, and a checking operation as illustrated in FIG. 18.

(54) FIG. 18 illustrates a method in which a return air temperature sensor, an outdoor air temperature sensor, and a supplied air temperature sensor are installed in the return air introduction chamber, the outdoor air introduction chamber, and the supplied air discharge chamber, respectively, and a defrosting operation, a normal operation, and a checking operation are performed on the basis of a result obtained by calculating the temperature exchange efficiency η using temperatures detected through the respective temperature sensors in a normal operation state.

(55) When the temperature exchange efficiency η becomes equal to or less than reference efficiency η.sub.S, the heat recovery ventilator determines that flow path blockage occurred in the exhaust air stream. When the temperature exchange efficiency η is lower than reference efficiency η.sub.S and when the outdoor temperature T.sub.OA is higher than ice formation reference temperature T.sub.S or a normal operation accumulating time RT is smaller than a reference time RT.sub.S, the heat recovery ventilator determines that flow path blockage occurred due to accumulated dust, issues an alarm, and performs a checking operation. The normal operation accumulating time RT indicates an accumulating time during which the normal operation is continuously performed without a defrosting operation.

(56) When the temperature exchange efficiency η is lower than reference efficiency η.sub.s and when the outdoor temperature T.sub.OA is lower than the ice formation reference temperature T.sub.S and the normal operation accumulating time RT is larger than the reference time RT.sub.S, the heat recovery ventilator determines that flow path blockage occurred due to ice formation, and starts a defrosting operation. After performing the defrosting operation for a preset time or more, the heat recovery ventilator resets the normal operation accumulating time RT, and then starts a normal operation.

(57) This method may be effectively used to determine whether the exhaust air flow path is normal or not when the supplied air flow path is normal, and performed at a low cost. However, this method cannot be used to determine whether the supplied air flow path is normal or not, and the defrosting operation time must be fixed because the defrosted state of the heat exchanger cannot be recognized during the defrosting operation.

(58) FIG. 19 illustrates a method in which two hole sensors capable of measuring a current flowing through an electric wire are used to perform a defrosting operation, a normal operation, and a checking operation.

(59) As shown in Table 4, when an air flow path is blocked, the resistance of the flow path is increased, and the amount of air flowing in the flow path is decreased. When the resistance of the flow path is increased, the amount of air transferred through a fan used in the heat recovery ventilator is decreased, and the rpm of the fan is increased. Then, the power consumption of the fan is reduced, and the amount of current supplied to the fan motor is reduced. That is, since the current amount of the fan is decreased in inverse proportion to the increase of the flow path resistance. Such a correlation constantly appears while the fan is used. Thus, when a hole sensor for measuring a current is installed in an electric wire for supplying power to the fan, the current may be measured to determine how much the flow path is blocked.

(60) FIG. 19 is a flow chart illustrating the method in which the heat recovery ventilator performs a defrosting operation, a normal operation, and a checking operation using two hole sensors installed in a supplied air fan and an exhaust air fan, respectively.

(61) When an exhaust air fan current I.sub.EA and a supplied air fan current I.sub.SA are larger than a normal operation exhaust air fan reference current I.sub.SEA and a normal operation supplied air fan reference current I.sub.SSA, the heat recovery ventilator performs a normal operation. When the exhaust air fan current I.sub.EA and the supplied air fan current I.sub.SA are smaller than the exhaust air fan reference current I.sub.SEA and the normal operation fan reference current I.sub.SSA, the heat recovery ventilator performs a defrosting operation. When the currents I.sub.EA and I.sub.SA are larger than a defrosting operation exhaust air fan reference current I.sub.DEA and a defrosting operation supplied air fan reference current I.sub.DSA, the heat recovery ventilator stops the defrosting operation, and returns to the normal operation. When the currents I.sub.EA and I.sub.SA are smaller than the reference currents I.sub.DEA and I.sub.DSA even though a defrosting operation time DT exceeds a time limit DT.sub.S, the heat recovery ventilator stops the defrosting operation, issues an alarm, and performs a checking operation.

(62) FIG. 20 illustrates a method in which the heat recovery ventilator performs a defrosting operation, a normal operation, and a checking operation using three temperature sensors and two hole sensors capable of measuring a current flowing through an electric wire.

(63) FIG. 20 illustrates a method in which the methods of FIGS. 18 and 19 are combined. According to the method, the heat recovery ventilator performs a defrosting operation, a normal operation, and a checking operation using a return air temperature sensor, an outdoor air temperature sensor, and a supplied air temperature sensor, which are installed in the return air introduction chamber, the outdoor air introduction chamber, and the supplied air discharge chamber, respectively, and the two hole sensors installed in the supplied air fan and the exhaust air fan, respectively.

(64) When the temperature exchange efficiency η is higher than the reference efficiency η.sub.S in a normal operation state and when the exhaust air fan current I.sub.EA and the supplied air fan current I.sub.SA are larger than the normal operation exhaust air fan reference current I.sub.SEA and the normal operation supplied air fan reference current I.sub.SSA, the heat recovery ventilator performs a normal operation. Otherwise, the heat recovery ventilator performs a defrosting operation or checking operation. When the operation state deviates from the normal operation condition and the outdoor air temperature T.sub.OA is lower than the ice formation reference temperature T.sub.S, the heat recovery ventilator performs a defrosting operation. When the outdoor air temperature T.sub.OA is higher than the ice formation reference temperature T.sub.S, the heat recovery ventilator issues an alarm, and starts a checking operation.

(65) When the currents I.sub.EA and I.sub.SA are larger than the defrosting operation exhaust air fan reference current I.sub.DEA and the defrosting operation supplied air fan reference current I.sub.DSA during the defrosting operation, the heat recovery ventilator stops the defrosting operation, and returns to the normal operation. When the currents I.sub.EA and I.sub.SA are smaller than the reference currents I.sub.DEA and I.sub.DSA even through the defrosting operation time DT exceeds the time limit DT.sub.S, the heat recovery ventilator stops the defrosting operation, issues an alarm, and performs a checking operation.

(66) While the present invention has been described with respect to the specific embodiments, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims.