Show case

Abstract

To provide a show case for appropriately controlling an output of a due condensation proof heater in accordance with a change of a peripheral environment so as not to generate due condensation and not to perform excessive heating.SOLUTION: A show case includes: a due condensation proof heater 15 arranged in a decorative frame 9 being a due condensation generation place of a show case body 4; detection means 12, 13 of peripheral temperature and peripheral moisture in the show case; and a heater control section 20 for controlling an electrification amount to the due condensation proof heater 15. The heater control section 20 controls the electrification amount to the due condensation proof heater 15 on the basis of dew-point temperature calculated based on the peripheral temperature and the peripheral moisture detected by the detection means 12, 13 and also on the basis of the peripheral temperature.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a showcase installed in stores such as convenience stores and supermarkets.

Background Art

[0002] As an example of a showcase installed in stores such as convenience stores and supermarkets, a flat open showcase described in Patent Document 1 is known. The showcase described in Patent Document 1 is a flat showcase having an opening at the upper part, and an anti-condensation heater is provided on the back side of the decorative frame in order to prevent condensation of the decorative frame provided at the periphery of the opening.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Since the decorative frame of the flat open showcase is in contact with the air in the store where the showcase is installed, condensation may occur or it may be overheated by the anti-condensation heater due to changes in the surrounding environment, which is the environment in the store. Therefore, it has been desired to appropriately control the output of the anti-condensation heater.

[0005] The present invention has been made in view of the above actual situation, and an object thereof is to provide a showcase that appropriately controls the output of the anti-condensation heater so as not to cause condensation or overheating in response to changes in the surrounding environment.

Means for Solving the Problems

[0006] One aspect of the present invention includes a dew prevention heater disposed at a location where dew condensation occurs in a showcase, a heater control unit that controls the amount of electricity supplied to the dew prevention heater, and a detection means for the ambient temperature and ambient humidity of the showcase. The heater control unit controls the amount of electricity supplied to the dew prevention heater based on the dew point temperature calculated based on the ambient temperature and ambient humidity detected by the detection means and the ambient temperature.

Advantages of the Invention

[0007] The present invention can provide a showcase that appropriately controls the output of the dew prevention heater so as not to cause dew condensation or overheating in response to changes in the ambient environment.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4A

Figure 4B

Figure 5

Embodiments for Carrying Out the Invention

[0009] Hereinafter, the showcase 1 according to the embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a perspective view of the showcase 1, and FIG. 2 is a plan view of the showcase 1 viewed from above. The showcase 1 is a flat open showcase having a rectangular opening 2 formed on the upper surface. The showcase 1 is installed in a store such as a supermarket or a convenience store, and frozen products, ice confections, etc. are displayed as products.

[0010] The showcase 1 includes a showcase body 4 having a product storage compartment 3 for storing products, and a machine room 5 disposed below the showcase body 4. The showcase body 4 is substantially rectangular parallelepiped in shape, and a rectangular opening 2 is formed on the upper surface side of the showcase body 4. The showcase body 4 has a pair of long heat insulation walls 6 and a pair of short heat insulation walls 7 disposed between the pair of long heat insulation walls 6. A partition plate 8 is disposed at a predetermined interval on the side of the product storage compartment 3 from the heat insulation wall 6. A ventilation passage (not shown) is formed between the heat insulation wall 6 and the partition plate 8, and the product storage compartment 3 and the ventilation passage are partitioned by the partition plate 8. An evaporator (not shown) for cooling air, a fan for circulating the cooled air, and an expansion valve are provided in the ventilation passage. A decorative frame 9 that covers the upper ends of the long heat insulation wall 6 and the partition plate 8 is provided at the longitudinal edge of the opening 2 formed in the showcase body 4. An air inlet 10 communicating with the ventilation passage is provided above the partition plate 8 and directly below the decorative frame 9, and an air outlet (not shown) is provided above the partition plate 8 facing the partition plate 8 where the air inlet 10 is provided. Further, an in-store temperature sensor 14 for detecting the in-store temperature is provided in the ventilation passage formed between the partition plate 8 and the heat insulation wall 6 on the side where the air inlet 10 is provided.

[0011] The machine room 5 is substantially rectangular parallelepiped in shape similar to the showcase body 4, and a compressor, a condenser, and a fan for promoting heat dissipation of the condenser (not shown) are provided in the machine room 5. A refrigeration circuit is formed by the compressor and the condenser provided in the machine room 5, and the evaporator and the expansion valve provided in the ventilation passage. The air (cold air) cooled by the evaporator is blown out from the air outlet, cools the products disposed in the product storage compartment 3, and then is sucked in from the air inlet 10 and cooled again by the evaporator. A so-called air curtain is formed above the product storage compartment 3 by the cold air blown out from the air outlet provided above the partition plate 8 and sucked into the air inlet 10 provided above the facing partition plate 8.

[0012] In the machine room 5, an air inlet 11 is provided for taking in ambient air, which is the air around the showcase 1, and the condenser is cooled by the ambient air taken in from the air inlet 11. Also, in the machine room 5, a temperature sensor 12 for detecting the ambient temperature, which is the temperature of the taken-in ambient air, and a humidity sensor 13 for detecting the ambient humidity, which is the humidity of the taken-in ambient air, are provided. The temperature sensor 12 and the humidity sensor 13 are the detection means in the present invention.

[0013] Since the air cooled by the evaporator blows out from the air outlet provided directly below the decorative frame 9, the decorative frame 9 covering the upper ends of the long heat insulating wall 6 and the partition plate 8 is cooled by the cooled air. Also, the upper part of the short heat insulating wall 7 is cooled by the cooled air. Since the decorative frame 9 and the upper part of the short heat insulating wall 7 are in contact with the air (ambient air) in the store where the showcase 1 is installed, there is a risk of condensation. Therefore, a dew prevention heater 15 is provided on the back surface on the top surface side of the decorative frame 9 and on the back surface, which is the surface opposite to the surface on the product storage 3 side at the upper part of the short heat insulating wall 7. In FIGS. 1 and 2, the dew prevention heater 15 is indicated by a two-dot chain line. Also, although not shown, a dew prevention heater 15 is also provided on the back surface of the surface of the decorative frame 9 on the product storage 3 side. Incidentally, the dew prevention heater 15 is provided on the back surface at the upper part of the short heat insulating wall 7, but in FIG. 2, it is shown at a position away from the back surface of the heat insulating wall 7 for easy understanding. The decorative frame 9 and the surface on the product storage 3 side at the upper part of the short heat insulating wall 7 are the locations where condensation occurs in the present invention.

[0014] The showcase 1 includes a heater control unit 20 that controls the amount of electricity supplied to the dew prevention heater 15, and a dew point temperature calculation unit 21 that calculates the dew point temperature based on the ambient temperature and humidity of the showcase 1. Each of the heater control unit 20 and the dew point temperature calculation unit 21 is composed of a CPU and a memory, and is arranged in the machine room 5. In the showcase 1 of the present embodiment, the heater control unit 20 outputs the energization rate as the amount of electricity supplied to the dew prevention heater 15, and controls the output of the dew prevention heater 15 by controlling the energization rate. In the present embodiment, the heater control unit 20 outputs the energization rate as the amount of electricity supplied to the dew prevention heater 15 and controls the energization rate, but is not necessarily limited to this. Other controls such as current control that outputs the current value as the amount of electricity supplied to the dew prevention heater 15 and controls the current value may be used to control the amount of electricity supplied.

[0015] Next, the control performed by the heater control unit 20 of the showcase 1 of the present embodiment will be described. Before that, the relationship between the air temperature (temperature), humidity (relative humidity), and dew point temperature will be described with reference to the graph shown in FIG. 3. FIG. 3 shows that the vertical axis represents the saturated water vapor amount, the horizontal axis represents the air temperature, the upward-sloping curve represents the saturated water vapor amount, and the hatched portion represents the amount of water vapor contained in the air (9.4 g / m 3 ). The air temperature, relative humidity, and dew point temperature are related such that if any two of them are known, the remaining one can be obtained. Therefore, even if the dew point temperature is the same, the air temperature may be different, and even if the dew point temperature is the same, the relative humidity may be different. As shown in the graph of FIG. 3, the relative humidity at an air temperature of 30°C is 31.0%, the relative humidity at an air temperature of 20°C is 54.4%, and the relative humidity at an air temperature of 10°C is 100%. Since the air temperature at which the relative humidity becomes 100% is the dew point temperature, the dew point temperature is 10°C. When the amount of water vapor contained in the air is 9.4 g / m 3 , the dew point temperature is 10°C. When the dew point temperature is 10°C as the same dew point temperature, it can be seen that the relative humidity (31.0%) at a higher air temperature (30°C) is lower than the relative humidity (54.4%) at a lower air temperature (20°C), or the air temperature (30°C) at a lower relative humidity (31.0%) is higher than the air temperature (20°C) at a higher relative humidity (54.4%).

[0016] Next, with reference to FIGS. 4A and 5, the control of the heater control unit 20 of the showcase 1 will be described. FIG. 4A is a control block diagram of the showcase 1. The heater control unit 20 controls the energization amount to the dew prevention heater 15. In the present embodiment, the energization amount is the energization rate. FIG. 5 is a graph showing the relationship between the dew point temperature, the air temperature, and the energization rate of the dew prevention heater 15 (hereinafter sometimes referred to as the output of the dew prevention heater 15) controlled by the heater control unit 20.

[0017] Conventionally, when controlling the dew prevention heater, since the heater control unit determined the output of the dew prevention heater based only on the dew point temperature regardless of the ambient temperature of the showcase, the output of the dew prevention heater might become excessive. Also, in order to detect whether the temperature of the dew formation location has become equal to or higher than the dew point temperature by the dew prevention heater, it was necessary to provide a temperature sensor at the dew formation location. However, in the showcase 1 of the present embodiment, when controlling the dew prevention heater, by considering not only the dew point temperature but also the ambient temperature (room temperature) of the showcase 1, it is not necessary to provide a temperature sensor at the dew formation location, and it can be derived that the output of the dew prevention heater can be suppressed compared to the case where the output of the dew prevention heater was determined based only on the dew point temperature. Hereinafter, specifically, the control of the heater control unit 20 of the showcase 1 will be described.

[0018] Figure 4A is a control block diagram of Showcase 1. Showcase 1 includes a dew prevention heater 15 disposed on the decorative frame 9, which is the location where dew condensation occurs in the showcase body 4, and the upper part of the short heat insulation wall 7, a heater control unit 20 that controls the amount of electricity supplied to the dew prevention heater 15, a temperature sensor 12 that detects the ambient temperature of Showcase 1, a humidity sensor 13 that detects the ambient humidity of Showcase 1, and a dew point temperature calculation unit 21 that calculates the dew point temperature based on the ambient temperature and ambient humidity of Showcase 1. The dew point temperature calculation unit 21 calculates the dew point temperature based on the ambient temperature of Showcase 1 detected by the temperature sensor 12 and the ambient humidity detected by the humidity sensor 13. The dew point temperature calculated by the dew point temperature calculation unit 21 and the ambient temperature detected by the temperature sensor 12 are input to the heater control unit 20. The heater control unit 20 controls the energization rate, which is the amount of electricity supplied to the dew prevention heater 15, based on the input dew point temperature and the input ambient temperature. Additionally, the amount of electricity supplied to the dew prevention heater 15 may also be controlled considering the internal temperature detected by the internal temperature sensor 14. In this embodiment, the heater control unit 20 and the dew point temperature calculation unit 21 have different configurations. However, for example, the heater control unit 20 may have a configuration that includes the dew point temperature calculation unit 21. In that case, the ambient temperature of Showcase 1 detected by the temperature sensor 12 and the ambient humidity detected by the humidity sensor 13 are input to the heater control unit 20. The dew point temperature calculation unit 21 included in the heater control unit 20 calculates the dew point temperature based on the ambient temperature of Showcase 1 input to the heater control unit 20 and the ambient humidity of Showcase 1. The heater control unit 20 controls the energization rate, which is the amount of electricity supplied to the dew prevention heater 15, based on the dew point temperature calculated by the dew point temperature calculation unit 21 and the ambient temperature input to the heater control unit 20.

[0019] Regarding specific control, reference is made to FIG. 5 for description. The graph in FIG. 5 shows the relationship between the dew point temperature (°C) and the energization rate (%) when the ambient temperature is fixed. The horizontal axis indicates the dew point temperature (°C), and the vertical axis indicates the energization rate (%). The solid line of the graph in FIG. 5 represents the energization rate when the ambient temperature is T1 and the temperature inside the product storage warehouse 3 is KT1, and the dotted line represents the energization rate when the ambient temperature is T2 and the temperature inside the warehouse is KT1. The dashed line represents the energization rate when the ambient temperature is T1 and the temperature inside the product storage warehouse 3 is KT2. T1 < T2 and KT1 < KT2. Note that in the showcase 1 of the present embodiment, since no temperature sensor is provided at the location where condensation occurs, the energization rate is a value obtained through experiments. The energization rate is the energization rate when the energization rate is changed at a certain dew point temperature and condensation no longer occurs at the location where condensation occurs on the showcase body 4. The dew point temperature is changed to obtain the energization rate at each dew point temperature. Since the energization rate is the energization rate in a state where condensation no longer occurs at the location where condensation occurs on the showcase body 4, it substantially represents the energization rate at a temperature of dew point temperature + α. The solid line and dotted line graphs show the relationship between the dew point temperature and the energization rate when the ambient temperature is different, and the solid line and dashed line graphs show the relationship between the dew point temperature and the energization rate at different internal temperatures of the warehouse at the same ambient temperature.

[0020] As can be seen from the graph, when the ambient temperature is the same, the lower the dew point temperature, the lower the amount of power supplied to the anti-condensation heater. That is, when the ambient temperature is the same, the higher the dew point temperature, the higher the amount of power supplied to the anti-condensation heater. At the dew point temperature TD2, the energization rate when the ambient temperature is T1 is R2H. On the other hand, at the same dew point temperature TD2, the energization rate when the ambient temperature is T2 (>T1) is R2L, which is lower than the energization rate R2H. That is, when the dew point temperature is the same and there is a difference in the ambient temperature, the energization rate when the ambient temperature is high is lower than the energization rate when the ambient temperature is low.

[0021] At the dew point temperature TD3, when the ambient temperature is T1 and the temperature inside the storage is KT1, the energization rate is R3H. On the other hand, at the same dew point temperature TD3, when the ambient temperature is T1 and the temperature inside the storage is KT2 (>KT1), the energization rate is R3L, which is lower than the energization rate R3H. That is, when the dew point temperature and the ambient temperature are the same but there is a difference in the temperature inside the storage, the energization rate when the temperature inside the storage is high is lower than the energization rate when the temperature inside the storage is low.

[0022] From this result, the heater control unit 20 controls the amount of power supplied to the dew condensation prevention heater 15 to decrease as the dew point temperature decreases when the ambient temperature is the same, and controls the amount of power supplied to the dew condensation prevention heater 15 to decrease as the ambient temperature increases when the dew point temperature is the same.

[0023] The heater control unit 20 has a memory (not shown), and the following control formula is stored in the memory. Based on the stored control formula, the heater control unit 20 controls the dew condensation prevention heater 15. The control formula is a graph shown in FIG. 5. That is, the control formula controls the amount of power supplied to the dew condensation prevention heater 15 to decrease as the dew point temperature decreases when the ambient temperature is the same, and controls the amount of power supplied to the dew condensation prevention heater 15 to decrease as the ambient temperature increases when the dew point temperature is the same. Y = A×TD(X)+B - C×T Y: Energization rate (%) TD(X): Dew point temperature (°C) A: Coefficient of the dew point temperature TD(X) B: Energization rate (%) when the dew point temperature is 0°C T: Ambient temperature (°C) C: Coefficient of the ambient temperature T Each coefficient is obtained from the surface temperature of the location where condensation is most likely to occur as a result of experiments. Thus, condensation will not occur in other locations. Incidentally, the coefficients may be obtained for each part, for example, for each of the decorative frame 9 where condensation occurs and the upper part of the short heat insulation wall 7, and the energization rate may be controlled for each part. Also, the upper limit value of the energization rate may be 100%, but for example, it may be set to the energization rate (for example, R3H (<100%)) in the case of the air temperature T1 and the dew point temperature TD in the most severe environment (for example, TD3). The lower limit value of the energization rate may be 0%, but for example, it may be set to the energization rate (for example, R1 (>0%)) in the case of the air temperature T1 and the dew point temperature TD in the mildest environment (for example, TD1).

[0024] The above control formula Y was a control formula that did not consider the temperature KT inside the cabinet, but the control formula Y may be the following formula that considers the ambient temperature T and the temperature KT inside the cabinet. Y = A × TD(X) + B - C × T - D × KT KT: Temperature inside the cabinet (°C) D: Coefficient of the temperature KT inside the cabinet

[0025] In the showcase 1 of the present embodiment, it includes a dew prevention heater 15 disposed at the location where condensation occurs in the showcase 1, a heater control unit 20 that controls the amount of power supplied to the dew prevention heater 15, and detection means for the ambient temperature and ambient humidity of the showcase 1. The heater control unit 20 controls the amount of power supplied to the dew prevention heater 15 based on the dew point temperature calculated based on the ambient temperature and ambient humidity detected by the detection means and the ambient temperature.

[0026] With this configuration, the output of the dew prevention heater 15 can be appropriately controlled in response to changes in the surrounding environment. In particular, in the case of a flat open showcase having a rectangular opening formed in the upper surface, the decorative frame provided at the periphery of the opening becomes a dew condensation occurrence portion. However, since the decorative frame is a place where a shopper touches with their hand, it may be difficult to install a temperature sensor. However, in the showcase 1 of the present embodiment, without providing a dedicated temperature sensor in the decorative frame 9 which is a dew condensation occurrence portion of the showcase 1, it is possible to prevent dew condensation in the decorative frame 9 and suppress the power consumption of the dew prevention heater 15 due to excessive heating of the dew prevention heater 15.

[0027] In addition, in the present embodiment, a temperature sensor 12 for detecting the ambient temperature and a humidity sensor 13 for detecting the ambient humidity are provided, and the dew point temperature is calculated based on the temperature detected by the temperature sensor 12 and the humidity detected by the humidity sensor 13. However, it is not necessarily limited to this. For example, without providing a humidity sensor, a temperature sensor 12 and a humidity setting means for deriving a standard relative humidity set in advance based on the ambient temperature detected by the temperature sensor 12 as the ambient humidity may be provided, and the dew point temperature may be calculated based on the ambient temperature detected by the temperature sensor 12 and the ambient humidity derived from the humidity setting means. In this case, the temperature sensor 12 and the humidity setting means are the detection means in the present invention.

[0028] Next, referring to FIG. 4B, the showcase 1 of another embodiment will be described. FIG. 4B is a control block diagram of the showcase 1 of another embodiment. In the showcase 1 of the first embodiment described above, the heater control unit 20 controlled the energization amount to the dew prevention heater 15 based on the dew point temperature calculated by the dew point temperature calculation unit 21 and the ambient temperature, but is not necessarily limited thereto. As shown in FIG. 3, the air temperature, relative humidity, and dew point temperature are in a relationship where if any two of them are known, the remaining one can be obtained. Therefore, even if the dew point temperature is the same, the air temperature may be different, and even if the dew point temperature is the same, the relative humidity may be different. Accordingly, the showcase 1 of another embodiment includes a dew prevention heater 15 disposed at the dew condensation occurrence location of the showcase main body 4, a heater control unit 20 that controls the energization amount to the dew prevention heater 15, and a dew point temperature calculation unit 21 that calculates the dew point temperature based on the ambient temperature and ambient humidity of the showcase 1. The heater control unit 20 controls the energization amount to the dew prevention heater 15 based on the dew point temperature calculated by the dew point temperature calculation unit 21 and the ambient humidity. Further, the energization amount to the dew prevention heater 15 may be controlled in consideration of the internal temperature detected by the internal temperature sensor 14 as well.

[0029] In the showcase 1 of another embodiment 1, when the ambient humidity is the same, the heater control unit 20 decreases the energization amount to the dew prevention heater 15 as the dew point temperature is lower. When the dew point temperature is the same and there is a difference in the ambient humidity, the energization amount to the dew prevention heater 15 when the ambient humidity is low is lower than the energization amount to the dew prevention heater 15 when the ambient humidity is high. That is, when the dew point temperature is the same, the energization amount to the dew prevention heater 15 is controlled to decrease as the ambient humidity is lower.

[0030] With this configuration, the output of the dew prevention heater 15 can be appropriately controlled in response to changes in the ambient environment.

[0031] Also, in other embodiments, a temperature sensor 12 for detecting the ambient temperature and a humidity sensor 13 for detecting the ambient humidity are provided, and the dew point temperature is calculated based on the temperature detected by the temperature sensor 12 and the humidity detected by the humidity sensor 13, but it is not necessarily limited thereto. For example, a temperature sensor may not be provided, and a humidity sensor 13 and a temperature setting means for deriving a preset standard relative temperature as the ambient temperature based on the ambient humidity detected by the humidity sensor 13 may be provided, and the dew point temperature may be calculated based on the ambient humidity detected by the humidity sensor 13 and the ambient temperature derived from the temperature setting means. In this case, the humidity sensor 13 and the temperature setting means are the detection means in the present invention.

[0032] Further, in the showcase 1 of the present embodiment, a dew prevention heater 15 is provided on the back surface of the decorative frame 9 that covers the upper ends of the pair of long heat insulation walls 6 and on the side surface of the product storage 3 at the upper part of the pair of short heat insulation walls 7, but it is not necessarily limited thereto. For example, the dew prevention heater 15 may be provided only on the decorative frame 9.

[0033] In the showcase 1 of the present embodiment, the temperature sensor 12 and the humidity sensor 13 are provided in the machine room 5 of the showcase 1, but it is not necessarily limited thereto. The temperature sensor 12 and the humidity sensor 13 may be installed in other parts of the showcase 1. Alternatively, the temperature sensor 12 and the humidity sensor 13 may be installed in the store where the showcase 1 is installed.

[0034] In the showcase 1 of the present embodiment, the decorative frame 9 and the side surface of the product storage 3 at the upper part of the short heat insulation wall 7 are taken as the dew condensation occurrence locations, but it is not necessarily limited thereto. The dew condensation occurrence location may be other parts of the showcase 1.

[0035] In addition, the showcase 1 of the present embodiment is a flat showcase having a substantially rectangular parallelepiped shape with an opening 2 formed on the upper surface, but is not necessarily limited thereto. The showcase 1 may be, for example, an open showcase in which an opening is formed on the front surface, the opening is not provided with a glass door, and an air curtain is formed in the opening, or a reach-in showcase provided with a glass door. In that case, a dew prevention heater 15 is incorporated in the door frame of the glass door to prevent dew condensation on the door frame. The dew prevention heater 15 may be disposed at a location where dew condensation occurs in the showcase.

[0036] As described above, some embodiments of the present invention have been described. It should be noted that the present invention is not limited to the above embodiments, and various modifications and changes are possible within the scope of the present invention.

Explanation of Reference Numerals

[0037] 1 Showcase 2 Opening 3 Product Storage 4 Showcase Body 5 Machine Room 6 Heat Insulation Wall (Long Side) 7 Heat Insulation Wall (Short Side) 8 Partition Board 9 Decorative Frame 10 Suction Port 11 Air Intake 12 Temperature Sensor 13 Humidity Sensor 14 Internal Temperature Sensor 15 Dew Prevention Heater 20 Heater Control Unit 21 Dew Point Temperature Calculation Unit

Claims

1. A dew prevention heater disposed at a dew condensation occurrence location of a showcase, a heater control unit that controls the amount of electricity supplied to the dew prevention heater, and a detection means for the ambient temperature and ambient humidity of the showcase, comprising: The heater control unit controls the amount of electricity supplied to the dew prevention heater based on the dew point temperature calculated based on the ambient temperature and ambient humidity detected by the detection means and the ambient temperature. The showcase is characterized by this.

2. The heater control unit: When the ambient temperature is the same, the lower the dew point temperature, the more the amount of electricity supplied to the dew prevention heater is decreased. When the dew point temperature is the same, the higher the ambient temperature, the more the amount of electricity supplied to the dew prevention heater is decreased. The showcase according to claim 1 is characterized by this.

3. The heater control unit further controls the amount of electricity supplied to the dew prevention heater based on the temperature inside the storage. The showcase according to claim 1 or 2 is characterized by this.

4. When the dew point temperature is the same, the higher the temperature inside the storage, the more the amount of electricity supplied to the dew prevention heater is decreased. The showcase according to claim 3 is characterized by this.

5. A dew prevention heater disposed at a dew condensation occurrence location of a showcase, a heater control unit that controls the amount of electricity supplied to the dew prevention heater, and a detection means for the ambient temperature and ambient humidity of the showcase, comprising: The heater control unit controls the amount of electricity supplied to the dew prevention heater based on the dew point temperature calculated based on the ambient temperature and ambient humidity detected by the detection means and the ambient humidity. The showcase is characterized by this.

6. The heater control unit: When the ambient humidity is the same, the lower the dew point temperature, the more the amount of electricity supplied to the dew prevention heater is decreased. When the dew point temperature is the same, the lower the ambient humidity, the more the amount of electricity supplied to the dew prevention heater is decreased. The showcase according to claim 5 is characterized by this.

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