JP2008051361A - Heat pump type water heater - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat pump type water heater capable of preventing degradation of heat-up performance by a defrosting operation. <P>SOLUTION: In this heat pump type water heater comprising an evaporator for exchanging heat between the atmospheric air and a refrigerant, an outside air temperature detecting means for detecting an outside air temperature, and an evaporator temperature detecting means for detecting a temperature of the evaporator, and performing the defrosting operation to remove the frost attached to the evaporator, a first conditional expression and a second conditional expression determined from correlation of the outside air temperature and the evaporator temperature are provided, the start of defrosting operation is judged on the basis of an area defined by the first conditional expression and the second conditional expression, and the first conditional expression and the second conditional expression are corrected by adding correction coefficients to the first conditional expression and the second conditional expression according the last defrosting operation time to correct the judgement area to start the defrosting operation, when the second and following defrosting operations are performed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a defrosting operation of a heat pump type water heater.

  Generally, in an evaporator of a heat pump type hot water heater, since the refrigerant absorbs heat from the atmosphere, the evaporator temperature is low. Therefore, when the outside air temperature is low (for example, 2 ° C. to 5 ° C. or less), the temperature of the evaporator becomes zero or less, and when moisture is present, it becomes frost and adheres to the evaporator. If the operation is continued after frost adherence, the frost grows further and the heat exchange capacity in the evaporator is hindered, and the heating capacity is gradually reduced. Operation was performed to prevent frost growth. In the conventional defrosting operation, the water circulation of the water-refrigerant heat exchanger is stopped, and the opening of the expansion valve is opened to send hot gas to the evaporator to melt the evaporator frost. However, since the defrosting operation is performed by stopping the circulation of water, it is equivalent to the operation with zero heating capacity, and high temperature water discharge cannot be performed immediately upon returning to the normal boiling operation. In other words, the defrosting operation contributes to a longer boiling operation time, and efficient defrosting operation is an important issue for shortening the boiling operation time.

  In other words, it is important to control the frosting amount of the evaporator at the start of the defrosting operation under all outside air temperature conditions where frosting occurs, and in order to solve such problems, In the frost operation, a first conditional expression and a second conditional expression that indicate the relationship between the outside air temperature X and the evaporator temperature Y are provided. If the frost operation start condition is satisfied, the defrost operation is started, or if the evaporator temperature is in the lower region of the second conditional expression, the defrost operation is started (for example, see Patent Document 1).

  FIG. 7 is a conceptual diagram showing start determination of a conventional defrosting operation. In FIG. 7, the first conditional expression: Y (evaporator temperature) = a · X (outside air temperature) + b, the second conditional expression: Y (evaporator temperature) = a · X (outside air temperature) + c, Ta ( The defrosting operation upper limit temperature) and Tb (defrosting operation lower limit temperature) are determined whether or not to perform the defrosting operation according to the detected values of the evaporator temperature and the outside air temperature in the regions A, B, and C. Was. In Patent Document 1, the region A: the defrosting operation is not performed, the region B: the defrosting operation is performed depending on the conditions, and the region C: the defrosting operation is performed unconditionally. A conventional method for defining the first conditional expression and the second conditional expression will be described with reference to FIG. It should be noted that when the outside air temperature is high and the evaporator temperature, which is the inner state of frost formation, is Ta or higher, the defrosting operation is not performed, and unnecessary defrosting operation can be prevented. In addition, when the evaporator temperature is Tb or less, the defrosting operation is surely performed. Even when the outside temperature detecting means is covered with frost or snow and the outside temperature cannot be acquired properly, the outside temperature is ignored. Then, since the defrosting operation is performed, it is possible to prevent the state where frosting has progressed from continuing.

FIG. 8 is a correlation diagram showing the correlation between the evaporator temperature and the outside air temperature when the hot water supply heating capacity is reduced from the maximum value. As shown in FIG. 8, it can be seen that there is a substantially linear correlation between the evaporator temperature and the outside air temperature when the hot water supply heating capacity is reduced from the maximum value (for example, 90% of the maximum heating capacity). . However, since it is known that the linear relationship between the evaporator temperature and the outside air temperature fluctuates due to the effects of the compressor speed, incoming water temperature, boiling temperature, fan speed, external humidity, etc. The defrosting operation cannot always be entered at an appropriate timing simply by using only a general relationship as a conditional expression for starting the defrosting operation. Therefore, the first conditional expression and the second conditional expression are obtained by moving the evaporator temperature parallel to the upper and lower sides of the substantially linear relationship Y = a · X by giving a margin above and below the evaporator temperature. Conditional expression: Y = a · X + b, second conditional expression: Y = a · X + c. In these conditional expressions, the result of taking into account the pressure loss of the evaporator caused by the rotational speed of the compressor is reflected in the coefficient to improve the accuracy of the defrosting operation.
JP 2006-145083 A

  However, in the conventional defrosting operation, it is determined whether or not to perform the defrosting operation using the first conditional expression and the second conditional expression that are primary expressions of the outside air temperature X and the evaporator temperature Y as parameters. Because the deviation of the set parameters affects the timing of performing the defrosting operation, there is a problem that the defrosting operation cannot always be executed at an appropriate timing when the set parameters are not appropriate or depending on environmental conditions. Was.

  This invention solves the said conventional subject, and it aims at providing the heat pump type water heater which can prevent the fall of the boiling performance by a defrost operation.

  In order to solve the above-described conventional problems, a heat pump type water heater of the present invention includes an evaporator for exchanging heat between the atmosphere and a refrigerant, an outside air temperature detecting means for detecting the outside air temperature, and an evaporator for detecting the evaporator temperature. A heat pump water heater having a defrosting operation that removes frost adhering to the evaporator, the first conditional expression and the second condition obtained from the correlation between the outside air temperature and the evaporator temperature When the start of the defrosting operation is determined based on the area formed by the first conditional expression and the second conditional expression, and the second and subsequent defrosting operations are performed, the previous defrosting operation time is Accordingly, the first conditional expression and the second conditional expression are corrected by adding a correction coefficient to the first conditional expression and the second conditional expression, and the determination area of the start of the defrosting operation is corrected, thereby correcting the previous condition. The amount of frost formation is appropriate from the defrosting operation time Can determine whether, can be corrected by a factor determined from the previous defrosting operation time when performing the next defrosting operation, it is possible to perform the defrosting operation at an appropriate timing. In addition, by providing the second conditional expression, the defrosting operation is performed even when the frost determination cannot be performed due to some influence, so that the progress of frost formation can be prevented.

  The heat pump type water heater of the present invention can prevent a decrease in boiling performance due to a defrosting operation.

  The heat pump type hot water heater of the first invention comprises an evaporator for exchanging heat between the atmosphere and the refrigerant, an outside air temperature detecting means for detecting the outside air temperature, and an evaporator temperature detecting means for detecting the evaporator temperature, In a heat pump type water heater having a defrosting operation for removing frost adhering to an evaporator, the heat pump type water heater has a first conditional expression and a second conditional expression obtained from a correlation between an outside air temperature and an evaporator temperature, When the start of the defrosting operation is determined based on the conditional expression and the region formed by the second conditional expression, and the second and subsequent defrosting operations are performed, the first conditional expression and By adding a correction coefficient to the second conditional expression, the first conditional expression and the second conditional expression are corrected, and the determination area of the start of the defrosting operation is corrected. Can determine if the amount is appropriate Can be corrected by a factor determined from the previous defrosting operation time when performing the next defrosting operation, it is possible to perform the defrosting operation at an appropriate timing. In addition, by providing the second conditional expression, the defrosting operation is performed even when the frost determination cannot be performed due to some influence, so that the progress of frost formation can be prevented.

  In the heat pump type hot water heater of the second invention, particularly in the first invention, when the previous defrosting operation time is longer than the predetermined time, the defrosting operation time is determined by the correction coefficient being a positive constant. Since it is determined that the amount of frost formation is large because it is longer than the predetermined time, and the conditional expression is corrected so that the defrosting operation can be easily performed, the defrosting operation can be performed at an appropriate timing.

  In the heat pump type hot water heater of the third invention, particularly in the first or second invention, when the previous defrosting operation time is shorter than the predetermined time, the correction coefficient is a negative constant, Since the operation time is shorter than the predetermined time, it is determined that the amount of frost formation is small, and the conditional expression is corrected so that the defrosting operation can be easily performed. Therefore, the defrosting operation can be performed at an appropriate timing.

  In the heat pump hot water heater of the fourth invention, particularly in the first to third inventions, an upper limit value and a lower limit value of the defrosting operation are provided, a region below the first conditional expression and the upper limit value, and the second When the outside air temperature and the evaporator temperature are located above the conditional expression and the lower limit value, the defrosting operation is started if the defrosting start condition is satisfied, the lower area than the first conditional expression and the upper limit value, and When the outside air temperature and the evaporator temperature are located in a region below the second conditional expression and the lower limit value, the defrosting operation is started unconditionally, and if the temperature exceeds the upper limit value, the defrosting operation is not performed. Therefore, it is possible to prevent the defrosting operation in a state where the outside air temperature is high and there is no frost formation, and if it is below the lower limit value, the thermistor that is the outside air temperature detecting means is covered with frost or snow, Even if the outside temperature cannot be obtained, the outside temperature Vision and, since the defrosting operation and the evaporator temperature is below the lower limit, it is possible to prevent the condition continues because of frost has progressed, it is possible to perform appropriate defrosting operation.

  In the heat pump type hot water heater of the fifth invention, particularly in the first to fourth inventions, the defrosting operation start condition is equal to or higher than a predetermined rate of change when the evaporator temperature is lowered. Since it can be determined whether clogging has occurred, a more appropriate frosting state can be grasped.

  In the heat pump hot water heater of the sixth invention, particularly in the first to fourth inventions, the defrosting operation start condition is continuously located for a predetermined time in the region below the first conditional expression and the upper limit value. Even when the outside humidity is low and it is not possible to judge whether the evaporator is clogged by the rate of change of the evaporator temperature, a certain period of time has passed in the lower region of the first conditional expression in which frosting has progressed to some extent. After that, since the defrosting operation is performed, it is possible to prevent the state where the frosting has progressed from continuing, and the defrosting operation can be performed.

  The heat pump type hot water heater of the seventh invention is the first to sixth inventions, in particular, even if the refrigerant pressure on the high pressure side becomes equal to or higher than the critical pressure, the water is deprived of heat and the refrigerant temperature decreases. Since it does not condense, it becomes easy to form a temperature difference between the refrigerant and water in the entire water-refrigerant heat exchanger, so that hot water can be obtained and the heat exchange rate can be increased.

  In the heat pump type hot water heater of the eighth invention, in particular, in the seventh invention, since the refrigerant to be used is carbon dioxide, the relatively inexpensive and stable carbon dioxide is used for the refrigerant, thereby suppressing the product cost. At the same time, reliability can be improved. In addition, carbon dioxide has an ozone depletion coefficient of zero and a global warming coefficient of about 1/700 of the alternative refrigerant HFC-407C, which is very small.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 is a configuration diagram of a main part of a heat pump type water heater in the present embodiment. In FIG. 1, the heat pump circuit of the heat pump type hot water heater in the present embodiment is configured by connecting an evaporator 61, a compressor 62, a water-refrigerant heat exchanger 65, and an expansion valve 63 in an annular shape with a refrigerant pipe. Then, air is circulated to the evaporator 61 by the blower 64, and heat exchange is performed between the atmosphere and the refrigerant. During the boiling operation, when the operation is continued for a long time, the temperature of the evaporator 61 decreases, and frost is generated and grows depending on conditions such as a low outside air temperature. At this time, when the operating speed of the compressor 62 is high, the pressure loss of the refrigerant between the inlet / outlet of the evaporator 61 is large, the refrigerant temperature at the outlet portion is greatly reduced, and frost growth is higher than that of other parts. Will also be faster. As the frost grows gradually, the ventilation resistance of the evaporator 61 increases, so the amount of heat exchange decreases and the hot water supply heating capacity decreases. The heat pump type water heater in the present embodiment determines frost formation by a microcomputer (electronic control unit) 68 based on detection values of a thermistor (evaporator temperature detection means) 66 and a thermistor (outside air temperature detection means) 67, and defrosts. Driving has begun.

  The operation and action of the heat pump type water heater configured as described above will be described below. The first defrosting operation is the same as the conventional method, and detailed description is omitted. In addition, in the conventional method, when the defrosting operation is performed when there is almost no decrease in capacity from the maximum heating capacity, the defrosting operation is frequently performed in a situation where the amount of frost formation is small, and the defrosting operation is performed with respect to the boiling operation time. Since the percentage of operation time increases and the boiling time decreases, the accumulated hot water heating capacity decreases and energy is required to increase the evaporator temperature for each defrost operation. Will do. On the other hand, when the defrosting operation is performed when the capacity reduction from the maximum heating capacity is large, the boiling operation time per cycle becomes longer, but the hot water heating capacity is reduced due to frosting, and only wasteful energy is consumed. In addition, since the frost is growing, the defrosting operation time is lengthened, and the generation of intermediate temperature water is promoted. Therefore, in consideration of the balance, a conditional expression must be obtained from the correlation between the evaporator temperature and the outside air temperature when a certain capacity falls from the maximum heating capacity. In the present embodiment, the first conditional expression: Y (evaporator temperature) = a · X (outside air temperature) + b, second from the correlation between the evaporator temperature and the outside air temperature at 90% of the maximum heating capacity. Conditional expressions: Y (evaporator temperature) = a · X (outside air temperature) + c coefficients a, b, and c are calculated, which almost coincides with the point at which the evaporator is clogged. Further, the coefficient may be calculated in consideration of the effects of the compressor rotational speed, the incoming water temperature, the boiling temperature, the fan speed, and the like. In this embodiment, the coefficient is replaced by the linear expression, but the quadratic expression or other polynomials are used. You can replace it with

  2 and 3 are diagrams showing a determination region for starting the defrosting operation in the present embodiment. That is, it shows an area for determining whether or not to perform the second and subsequent defrosting operations. As shown in FIGS. 2 and 3, the first conditional expression and the second conditional expression are corrected by the correction coefficient e. FIG. 2 is a diagram showing a determination region when the correction coefficient e is corrected with a positive constant, and FIG. 3 is a diagram showing a determination region when the correction coefficient e is corrected with a negative constant. The correction coefficient e is determined based on whether the previous defrosting operation is longer or shorter than the predetermined time. When the defrosting operation time is longer than the predetermined time, the correction coefficient e is a positive constant, and the defrosting is longer than the predetermined time. When the operation time is short, the correction coefficient e is a negative constant. In other words, when the defrosting operation time is longer than the predetermined time, it is determined that the amount of frost formation is large, the condition is set to be easier to start the defrosting operation, and the defrosting operation time is shorter than the predetermined time. Since it is judged that the amount of frost formation is small and the defrosting operation may be delayed, the conditions are set strictly. By correcting in this way, the defrosting operation can be started at an appropriate timing in the second and subsequent defrosting operations.

  FIG. 4 is a control flowchart for starting the defrosting operation in the present embodiment. When the boiling operation is performed in FIG. 4, it is determined whether or not it is located in the region A (see FIGS. 2 and 3) in step 41. If it is in the region A, the boiling operation is continued. Go to 42.

  In step 42, it is determined whether or not the vehicle is located in the region B. If it is in the region B, the process proceeds to step 43. If it is not in the region B, the defrosting operation is started.

In step 43, it is determined whether the absolute value | ΔT | of the evaporator temperature change rate is larger than a predetermined value ΔTi and the evaporator temperature change rate ΔT is negative. The defrosting operation is started, and if the condition is not satisfied, the process proceeds to step 44.

  In step 44, it is determined whether or not a predetermined time (for example, 20 minutes) has elapsed in the region B. If the condition is satisfied, the defrosting operation is started. If the condition is not satisfied, the process proceeds to step 42. move on.

  Here, step 43 will be described in detail. FIG. 5 is a correlation diagram of the hot water supply heating capacity / evaporator temperature and the operation time in a normal time with the hot water supply heating capacity / evaporator temperature plotted on the vertical axis and the operation time plotted on the horizontal axis. In FIG. 5, it can be seen that the hot water heating capacity and the evaporator temperature are drastically dropping from a certain point. This indicates that the evaporator is beginning to clog due to frost, and the rate of change of the evaporator temperature is The defrosting operation can be performed with high accuracy by using the determination condition for starting the defrosting operation. However, if the defrosting operation is started under this condition when located in the area A, the evaporator temperature suddenly drops for some reason, the frost is not formed, or the frost is hardly formed In this embodiment, the defrosting operation start condition in region B is used in order to start the defrosting operation.

  Step 44 will be described in detail. FIG. 6 is a correlation diagram of hot water heating capacity / evaporator temperature and operating time at low humidity with the vertical axis representing hot water heating capacity / evaporator temperature and the horizontal axis plotted operating time. In FIG. 6, the time change of the hot water supply heating capacity and the evaporator temperature when the external humidity is low (for example, 70% or less) is shown. As shown in FIG. 6, when the humidity is low, since a rapid decrease in the evaporator temperature cannot be seen, the change rate of the evaporator temperature in step 43 cannot be used as a judgment material for starting the defrosting operation. . However, since it is expected that frost is formed to some extent when it is located in the region B, it is not preferable that such a state continues for a long time, leading to a decrease in the accumulated hot water heating capability. Therefore, the defrosting operation is started when a predetermined time (for example, 20 minutes) elapses, which is located in the region B. In addition, what is necessary is just to determine predetermined time so that accumulated hot water supply heating capability may become the maximum.

  As described above, by setting the next defrosting operation start condition according to the previous defrosting operation time, the defrosting operation can be started at an appropriate timing. Therefore, it is possible to prevent the boiling time from being prolonged.

  As described above, the determination control of the start of the defrosting operation in the heat pump type hot water heater according to the present invention is performed by the integrated heat pump type hot water heater in which the hot water storage tank and the heat pump cycle are configured integrally, the water-refrigerant heat exchanger. It can also be applied to the instantaneous water heating operation in which hot water is discharged as it is.

Configuration diagram of heat pump water heater in Embodiment 1 Defrosting operation start determination area (corrected with correction coefficient e> 0) in the first embodiment Defrosting operation start determination area (corrected with correction coefficient e <0) in the first embodiment Defrosting operation start determination control flowchart in the first embodiment Correlation diagram of hot water heating capacity / evaporator temperature and operation time in normal time in Embodiment 1 Correlation diagram of hot water supply heating capacity / evaporator temperature and operation time at low humidity in the first embodiment Start determination area diagram of defrosting operation in conventional form Correlation diagram between evaporator temperature and outside air temperature in conventional configuration

Explanation of symbols

61 Evaporator 62 Compressor 63 Expansion Valve 64 Blower 65 Water Refrigerant Heat Exchanger 66 Thermistor (Evaporator Temperature Detection Means)
67 Thermistor (Outside air temperature detection means)
68 Microcomputer (electronic control unit)

Claims (8)

A defrosting operation comprising an evaporator for exchanging heat between the atmosphere and the refrigerant, an outside air temperature detecting means for detecting the outside air temperature, and an evaporator temperature detecting means for detecting the evaporator temperature, and removing frost adhering to the evaporator. In the heat pump water heater having the above, the first conditional expression and the second conditional expression obtained from the correlation between the outside air temperature and the evaporator temperature are included, and the first conditional expression and the second conditional expression are The start of the defrosting operation is determined according to the area to be formed, and when performing the second and subsequent defrosting operations, a correction coefficient is added to the first conditional expression and the second conditional expression according to the previous defrosting operation time. The heat pump type hot water heater is characterized in that the first conditional expression and the second conditional expression are corrected by and the determination area of the start of the defrosting operation is corrected. The heat pump type hot water heater according to claim 1, wherein when the last defrosting operation time is longer than a predetermined time, the correction coefficient is a positive constant. The heat pump type hot water heater according to claim 1 or 2, wherein when the previous defrosting operation time is shorter than a predetermined time, the correction coefficient is a negative constant. When the upper limit value and the lower limit value of the defrosting operation are provided, and the outside air temperature and the evaporator temperature are located in a region below the first conditional expression and the upper limit value, and above the second conditional expression and the lower limit value, If the defrosting start condition is satisfied, the defrosting operation is started, and the outside air temperature and the evaporator temperature are located below the first conditional expression and the upper limit value, and below the second conditional expression and the lower limit value. The heat pump type hot water heater according to any one of claims 1 to 3, wherein the defrosting operation is started unconditionally. The heat pump hot water heater according to claim 4, wherein the defrosting operation start condition is equal to or higher than a predetermined rate of change when the evaporator temperature is lowered. The heat pump type hot water heater according to claim 4, wherein the defrosting operation start condition is continuously located for a predetermined time in a region below the first conditional expression and the upper limit value. The heat pump type water heater according to any one of claims 1 to 6, wherein the refrigerant pressure on the high pressure side is equal to or higher than a critical pressure. The heat pump type water heater according to claim 7, wherein the refrigerant to be used is carbon dioxide.

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