JP2013122340A - Hot water storage tank and heat pump type hot water supply machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress scale from sticking to a heat exchanger, in a hot water storage tank having the heat exchanger therein.SOLUTION: The hot water storage tank has a hot water storage tank body having a water supply channel and a hot water discharge channel, the heat exchanger arranged in the hot water storage tank and exchanging heat between a refrigerant flowing through the inside of the tank and water in the hot water storage tank, an electrode arranged in the hot water storage tank, and a power source connecting the heat exchanger and the electrode. The power source energizes the heat exchanger and the electrode, thereby the electrode functions as a positive electrode and the heat exchanger functions as the negative electrode relative to the electrode, or the electrode functions as the negative electrode and the heat exchanger functions as the positive electrode relative to the electrode. It is possible to suppress the scale from sticking to the heat exchanger and accordingly it is also possible to suppress heat exchanging efficiency from being lowered in use for a long period by making the heat exchanger itself function as the electrode.

Description

  The present invention relates to a hot water storage tank having a heat exchanger therein, and a heat pump hot water hot water heater using the hot water storage tank.

  As a heating method of a heat pump type hot water hot water heater using a refrigerant, the refrigerant from the heat source unit is supplied to the heat exchanger provided in the hot water storage tank, and the heat from the refrigerant to the water in the hot water tank is supplied through the heat exchanger. Some heat the water in a hot water tank by giving calories. When the water in the hot water storage tank is heated, dissolved salts in the water are concentrated in the process of heating the water, and the concentration increases. As a result, scale components typified by calcium carbonate and silica are deposited and fixed to the heat exchanger, resulting in a decrease in heat transfer efficiency. In particular, calcium carbonate precipitates more remarkably at a water temperature of 45 ° C. or higher, and therefore adheres very easily to the heat exchanger, causing a decrease in heat exchange efficiency. On the other hand, since silica precipitates when the acidity rises, it becomes a problem in circulation system piping and the like.

  In order to solve such a problem, there is a method for suppressing the sticking of the scale by introducing a chemical such as a scale inhibitor. However, when the purpose of using the hot water supply is for home use and is used directly on the human body, there is a possibility of rough skin or ingestion by the added medicine.

  As a scale prevention method that does not use a chemical, there is a method in which carbon dioxide dissolved in water is reacted with metal ions eluted in water to suppress the formation and precipitation of calcium carbonate in the heating section. For example, an electric current is generated between a pair of metal electrodes, and metal ions of aluminum ions having an effect of preventing scale are eluted in water. Since aluminum ions suppress the formation and precipitation of calcium carbonate, by using stainless steel and aluminum or carbon and aluminum for the cathode and anode, aluminum is eluted in the water and the adhesion of scale to the heat exchanger is suppressed. Can do. There is also a method for preventing scale by applying a direct current voltage to a pair of copper electrodes using an external power source to elute copper ions (see Patent Document 1).

  On the other hand, in a heat pump hot water water heater having a heat exchanger for heating in a tank, a scale mainly composed of calcium carbonate adheres to the heat exchanger due to long-term use, and a decrease in heat exchange efficiency is inevitable. Under continuous and long-term operating conditions, it is difficult to avoid adhesion of scales to the heat exchanger, which is the main heating unit, even using the technique disclosed in Patent Document 1.

JP-A-6-296970

  This invention makes it a subject to suppress adhesion of the scale to a heat exchanger in the hot water storage tank provided with a heat exchanger inside.

  The hot water storage tank of the present invention includes a hot water storage tank main body having a water supply port and a hot water outlet, a heat exchanger that is arranged in the hot water storage tank main body and exchanges heat between water flowing in the hot water storage tank and water in the hot water storage tank, An electrode disposed on the heat exchanger and a power supply unit that connects the heat exchanger and the electrode. The power supply unit energizes the heat exchanger and the electrode, whereby the electrode functions as an anode electrode and the heat exchanger serves as a cathode for the electrode. It functions as an electrode, or the electrode functions as a cathode electrode and the heat exchanger functions as an anode electrode for the electrode.

  ADVANTAGE OF THE INVENTION According to this invention, by making heat exchanger itself function as an electrode, scale adhesion to a heat exchanger can be suppressed and the fall of the heat exchange efficiency in long-term use can also be suppressed.

Schematic of a heat pump type hot water heater. Schematic of a hot water storage tank. The figure which electrically connected the sacrificial anode and the hot water storage tank main body. The figure which has arrange | positioned adsorption agent. The figure which shows the relationship between the distance and voltage of a heat exchanger and a sacrificial anode. The figure which shows the positional relationship of the heat exchanger and sacrificial anode with respect to a hot water storage tank.

  A first embodiment of the present invention will be described with reference to FIGS. 1, 2, and 4-6. FIG. 2 is a schematic diagram of the heat pump type hot water heater of this embodiment. The function on the left side of the refrigeration cycle shown in FIG. 2 is generally the same as that of the outdoor unit of the air conditioner during heating operation. That is, the heat pump type hot water hot water heater of the present embodiment includes a compressor 9 that compresses the refrigerant to a high temperature and a high pressure, a four-way valve 10 that switches between cooling and heating, and an atmospheric heat exchanger 11 that absorbs heat from the atmosphere by heat pump heating operation. And the refrigerating cycle is comprised by the expansion valve 12 which controls the pressure state of a refrigerant | coolant. In consideration of only hot water supply, the four-way valve 10 is not always necessary.

  These are connected to the hot water storage tank 1 on the right side of FIG. A high-temperature and high-pressure refrigerant is caused to flow into the heat exchanger 4 in the hot water storage tank 1 by heat pump operation to exchange heat with the water in the tank, and the water in the tank is heated to make hot water.

  Water is supplied into the hot water storage tank 1 from a water supply port connected to the water supply path 3 to maintain a full state. When the user uses a water supply facility such as a shower, hot water is supplied from the hot water outlet to the water supply facility via the hot water supply route 2, and the amount of water used is newly supplied from the water supply route 3. The temperature of the supplied water is detected by a plurality of temperature detection devices (not shown) arranged in the hot water storage tank 1, and a control unit (not shown) controls the operation of the compressor 9 based on the detection result. To do.

  FIG. 1 is a schematic view of a hot water storage tank of the present embodiment. The hot water storage tank 1 is provided with a hot water discharge path 2 at the upper part of the hot water storage tank 1 and the hot water storage tank 1 is provided with a water supply path 3 at the lower part of the hot water storage tank 1.

  A heat exchanger 4 to which a high-temperature and high-pressure refrigerant discharged from the compressor 9 is supplied is disposed in the hot water storage tank 1, and the heat exchanger 4 is fixed to the hot water storage tank 1 through a heat exchanger insulating portion 5. . A sacrificial anode 6 is disposed below the heat exchanger 4 in the hot water storage tank 1, and the sacrificial anode 6 is fixed to the hot water storage tank 1 via a sacrificial anode insulating portion 7. The heat exchanger insulating part 5 and the sacrificial anode insulating part 7 are provided in order not to make the hot water tank 1 into an energizing circuit. The DC power supply unit 8 includes an electronically controlled switch, and applies a voltage to the heat exchanger 4 and the sacrificial anode 6 according to a command from the control unit.

  The water in the hot water storage tank 1 heated by the heat exchanger 4 has a reduced density and circulates toward the upper part in the hot water storage tank 1. Accordingly, water having a relatively low temperature collects around the heat exchanger 4 arranged below the hot water storage tank 1, so that the heating efficiency is good.

  However, since the heat exchanger 4 itself is heated by the high-temperature and high-pressure refrigerant discharged from the compressor 9, the calcium ion concentration is increased around the heat exchanger 4 and calcium carbonate is deposited.

  On the other hand, when a voltage is applied to the heat exchanger 4 and the sacrificial anode 6 from the DC power supply unit 8, metal ions are eluted from the sacrificial anode 6 and taken into water. As a result, the metal ions eluted from the sacrificial anode 6 and carbon dioxide in the water are combined first to form a powdery scale.

  For example, when aluminum is used for the sacrificial anode 6, the combined substance with carbon dioxide in water is aluminum carbonate, and since this aluminum carbonate is an undefined basic salt, hydroxide in water is used as a transient product. It further reacts with ions to form aluminum hydroxide. Since aluminum hydroxide is insoluble in water and has no stickiness, it is generated around the sacrificial anode 6 and then deposited as sludge in the form of powder at the lower part of the hot water storage tank 1.

  Sludge accumulated at the bottom of the hot water storage tank 1 can be easily removed by cleaning. Moreover, even if it uses the filter type water purifier attached to the water supply equipment, it can be removed. For the sacrificial anode 6, for example, iron, zinc, copper, or an alloy thereof can be used in addition to aluminum.

  As described above, in the vicinity of the sacrificial anode 6, the dissolved carbon dioxide is allowed to react transiently, thereby inhibiting continuous binding with calcium ions and suppressing the precipitation of calcium carbonate scale. Moreover, the main material of the heat exchanger 4 is copper having an ionization coefficient smaller than that of the anode, and the surface treatment is tin or nickel having an ionization coefficient smaller than that of the anode, so that the cathode (heat exchanger 4) can supply electrons. Water is electrolyzed and the generation / incentive of hydrogen ions and gaseous hydrogen is excited, increasing the pH around the heat exchanger 4. By increasing the pH around the heat exchanger 4, it is possible to suppress the movement of calcium ions to the periphery of the heat exchanger 4. Therefore, in addition to the decrease in the concentration of calcium ions, the binding between calcium ions and carbon dioxide is suppressed, and the movement of calcium ions to the periphery of the heat exchanger 4 is suppressed. Scale adhesion can be suppressed.

  Furthermore, even if calcium ions are reduced at the cathode and single calcium is generated, unlike calcium carbonate, it is deposited on the bottom of the hot water storage tank 1 without being fixed to the heat exchanger.

  Furthermore, since the generation of local silica scale can be suppressed by increasing the pH, the overall scale suppression effect is high. Tap water is generally not derived from geothermal hot water, but since silica deposition is not zero, a certain effect can be expected.

  By these principles, the adhesion of the scale to the heat exchanger 4 is strongly suppressed, and a decrease in the heat exchange efficiency of the heat exchanger 4 during long-term use can be avoided.

  In this embodiment, the heat exchanger 4 is a cathode electrode with respect to the sacrificial anode 6, but the polarity of these anode electrode and cathode electrode may be reversed by the DC power supply unit 8.

  Further, as a result of examination by the inventors, it has been found that suitable anticorrosion and scale prevention effects can be obtained by controlling on / off of the DC power supply based on water temperature information by a temperature detection device (not shown). Specifically, when the water temperature at the tip of the heat exchanger is 40 to 85 degrees Celsius, more effective anticorrosion and scale prevention can be obtained.

  FIG. 5 is a diagram showing the relationship between the distance between the heat exchanger and the sacrificial anode and the voltage. As a result of examination by the inventors, it has been found that there is a suitable relationship between the applied voltage and the distance between the electrodes (the distance between the tip of the heat exchanger 4 and the center of the sacrificial anode 6 in the height direction). Specifically, when the distance between the electrodes is 25 centimeters to 80 centimeters, an applied voltage of about 1.5 V to 5.0 V is sufficient. In this case, the electrolytic reaction proceeds too much and the amount of hydrogen and chlorine generated increases, which impairs the convenience for the user. Therefore, the distance between the electrodes (distance between the tip of the heat exchanger 4 and the center of the sacrificial anode 6 in the height direction) is 25 to 80 cm, and the voltage applied to the heat exchanger 4 and the sacrificial anode 6 is 1.5 to 5 cm. About 0.0V is desirable.

  FIG. 6 is a diagram showing the positional relationship between the heat exchanger and the sacrificial anode with respect to the hot water storage tank. As a result of the examination by the inventors, it has been found that there is a preferable positional relationship with respect to the arrangement of the heat exchanger 4 and the sacrificial anode 6 with respect to the hot water storage tank 1. Specifically, when the hot water storage tank 1 is divided into approximately five equal parts in the height direction, and 1/5, 2/5, 3/5, 4/5, 5/5 from the bottom surface of the hot water storage tank 1, the heat exchanger 4 The refrigerant introduction portion is approximately 1/5 to 2/5 of the hot water storage tank 1, and the front end (the deepest portion) of the heat exchanger 4 is approximately from the bottom of the hot water storage tank 1 to 1/5 of the hot water storage tank 1. In this position, the sacrificial anode 6 was disposed approximately at the position of 2/5 to 3/5 of the hot water storage tank 1, so that a good scale prevention effect and heat exchange efficiency could be obtained.

  Here, the heat exchanger 4 can be made into the double pipe structure provided with a leak detection mechanism. Thereby, leakage of the refrigerant and water can be detected, and the refrigerant inflow portion and the energization portion can be completely separated. In general, it has been found that current passes through the surface layer. Also in the heat exchanger, the current from the DC power supply unit 8 flows through the surface layer of the heat exchanger. On the other hand, sudden inflow of current may cause unintended sparks. By using a double pipe for the heat exchanger 4, the possibility of the ignition of the refrigerant due to the generation of these sparks can be extremely reduced. Even if the refrigerant leaks, if it is a double pipe type leak detection pipe, the refrigerant will flow out into the hot water storage tank 1 and the pressure will rise rapidly, or it may be included in the refrigeration cycle. Therefore, the safety of the user is greatly improved. Even if it is a leak from the water side of the hot water storage tank 1, the refrigeration cycle and water are not mixed, so that repair is easy.

  Furthermore, a space for collecting gas may be provided in the upper part of the hot water storage tank 1 or in the route of the hot water supply route 2, and an adsorbent that adsorbs at least hydrogen or chlorine may be disposed in the space. In this embodiment, since an electrolytic circuit is used, the water itself is electrolyzed due to impurities in the water. For this reason, in the practice of the present invention, hydrogen generated by electrolysis of water and chlorine used for disinfection are expected, and the inventors have confirmed the generation of hydrogen and chlorine. These gases are released from faucets etc. when the user uses hot water, but if they remain in the piping, they may cause pressure fluctuations or poor water distribution due to air locks, so remove them as much as possible. It is desirable. Therefore, in this embodiment, a trap for collecting gas is provided in the upper part of the hot water storage tank 1 or in the outlet hot water path 2, and an adsorbent that adsorbs at least hydrogen or chlorine is disposed in the space, so The generated hydrogen and chlorine will be removed.

  As described above, the hot water storage tank of the present embodiment includes a hot water storage tank body having a water supply path and a hot water discharge path, a heat exchanger that is disposed in the hot water storage tank body and that exchanges heat between water flowing in the hot water storage tank and water in the hot water storage tank, An electrode disposed in the tank body and a power supply unit that connects the heat exchanger and the electrode, and the power supply unit energizes the heat exchanger and the electrode so that the electrode functions as an anode electrode and the heat exchanger It functions as a cathode electrode for the electrode, or the electrode functions as a cathode electrode and the heat exchanger functions as an anode electrode for the electrode. By causing the heat exchanger itself to function as an electrode, scale adhesion to the heat exchanger can be suppressed. In particular, in addition to a decrease in the concentration of calcium ions, the binding between calcium ions and carbon dioxide is suppressed, and the movement of calcium ions to the heat exchanger is suppressed, so that the scale adheres to the heat exchanger. Can be suppressed. Therefore, the fall of the heat exchange efficiency of the heat exchanger in a long-term use can also be suppressed. In addition, since the heat exchanger itself is used as an electrode, an anode / cathode is not required separately and can be constructed at low cost.

  Next, a second embodiment of the present invention will be described with reference to FIG. Since the basic refrigeration cycle, hot water storage tank, and the like are configured in the same manner as in the first embodiment, differences from the first embodiment will be described.

  In the first embodiment, a DC voltage is applied from the DC power supply unit 8 to the heat exchanger 4 and the sacrificial anode 6, but when no voltage is applied to the heat exchanger 4 and the sacrificial anode 6, the sacrificial anode 6 and the hot water storage tank 1 main body are connected. A circuit is constructed so that it can be electrically connected (so that the sacrificial anode 6 and the metal part of the hot water storage tank 1 can be connected). By electrically connecting the sacrificial anode 6 and the hot water storage tank 1, the anticorrosion effect of the hot water storage tank 1 (generally stainless steel) can be obtained without application of voltage. At this time, since the same copper material as the heat exchanger 4 cannot be used as the material of the sacrificial anode 6, it is preferable to use aluminum, zinc, or an alloy thereof.

DESCRIPTION OF SYMBOLS 1 Hot water storage tank 2 Hot water supply path 3 Water supply path 4 Heat exchanger 5 Heat exchanger insulation part 6 Sacrificial anode 7 Sacrificial anode insulation part 8 DC power supply part 9 Compressor 10 Four-way valve 11 Atmospheric side heat exchanger 12 Expansion valve 13 Adsorbent

Claims (10)

A hot water storage tank body having a water inlet and a hot water outlet;
A heat exchanger disposed in the hot water storage tank body for exchanging heat between the refrigerant flowing inside and the water in the hot water storage tank;
An electrode disposed in the hot water storage tank body;
A power supply unit connecting the heat exchanger and the electrode,
When the power supply unit energizes the heat exchanger and the electrode,
The electrode functions as an anode electrode, and the heat exchanger functions as a cathode electrode for the electrode, or
A hot water storage tank in which the electrode functions as a cathode electrode and the heat exchanger functions as an anode electrode for the electrode. In claim 1, the heat exchanger is made of copper,
The electrode is made of copper, iron, aluminum, zinc, or an alloy thereof,
A hot water storage tank in which the electrode functions as an anode electrode and the heat exchanger functions as a cathode electrode for the electrode by energizing the heat exchanger and the electrode by the power supply unit.   The hot water storage tank according to claim 1 or 2, wherein the power supply unit reverses the polarity of the anode electrode and the cathode electrode. In any one of Claims 1 thru | or 3, the said electrode is comprised with aluminum, zinc, or these alloys,
A hot water storage tank in which the power supply unit does not energize the heat exchanger and the electrode, and the electrode and the hot water storage tank body are electrically connected.   5. The hot water storage tank according to claim 1, wherein when the water temperature at the front end portion of the heat exchanger is 40 to 85 degrees Celsius, the power supply unit energizes the heat exchanger and the electrode.   The voltage applied by the power supply unit according to any one of claims 1 to 5 is 1.2 to 5.0 V, and a distance between a tip portion of the heat exchanger and a center in the height direction of the electrode is 25 to 80. A hot water storage tank that is centimeters.   7. The hot water storage tank according to claim 1, wherein the heat exchanger has a double pipe structure provided with a leakage detection mechanism.   The adsorption according to any one of claims 1 to 7, wherein a space for collecting gas is provided in an upper part of the hot water storage tank body or in a hot water outlet path connected to the hot water outlet, and at least hydrogen or chlorine is adsorbed in the space. Hot water storage tank to place the agent. In any one of Claims 1 thru | or 8, When the height direction of the said hot water storage tank main body is divided into five equal parts,
The center of the electrode is located at a height of 2/5 to 3/5 of the hot water storage tank from the bottom surface of the hot water storage tank,
The front end of the heat exchanger is located at the bottom of the hot water storage tank to 1/5 height of the hot water storage tank,
The hot water storage tank in which the refrigerant introduction part of the heat exchanger is located at a height of 1/5 to 2/5 of the hot water storage tank from the bottom surface of the hot water storage tank. The hot water storage tank according to any one of claims 1 to 9, and
The heat exchanger disposed in the hot water storage tank, a compressor that compresses the refrigerant to high temperature and high pressure, an atmosphere-side heat exchanger that absorbs heat from the atmosphere by heat pump operation, and an expansion that controls the pressure state of the refrigerant A refrigeration cycle apparatus configured by connecting a valve,
A heat pump type hot water hot water supply machine.