JPH0539966A - Heat pump device - Google Patents

Abstract

PURPOSE:To greatly heighten the utility of the title device using Peltier effect by sharply improving critical efficiency settled by a performance index for a thermoelectric material used, with regard to the improvement of a heat pump. CONSTITUTION:For a definite time, an electric current is applied to a heat- radiation device composed so as to be the same as a heat-absorption device, which consists of a semiconductor 2, a copper plate 3 used as an electrode and heat-exchange fins 4, in the state in which one semiconductor end-surface 10 is electrically joined to the other. After that, the heat-radiation device is spatially separated from the end-surface 10 by a driving motor 9 and heat in these semiconductors is isolated each other before each interior of these semiconductors respectively reaches a thermally stable state.

Description

Detailed Description of the Invention

[0001]

The present invention utilizes the Peltier effect,
In particular, the present invention relates to a heat pump device used in an air conditioner for electrically cooling or heating.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 4, a basic structure of a heat pump device for converting electricity into heat is a metal plate 13 also serving as a current terminal, and an N-type semiconductor 15 which is a thermoelectric material by a metal plate 14, or The P-type semiconductor 16 is sandwiched and heated by Peltier heat by passing an electric current,
It is for cooling.

The conventional example of FIG. 4 is a thermoelectric element in which N-type semiconductors 15 and P-type semiconductors 16 are alternately arranged in series.
When an electric current is applied, one of the metal plates is cooled and the other is heated. It has been used as a heat pump for cooling and heating by exchanging heat with the outside air by a heat exchanger 17 arranged on those metal plates.

[0004]

However, in the basic structure of the conventional heat pump device, the Seebeck coefficient (α) and the electric conductivity (σ) of the thermoelectric material used are
And the figure of merit (Z; Z = α) determined from the thermal conductivity (κ)
² · σ / κ) has a limit of efficiency, and Z = 2.5 × 10 even for Bi ₂ Te ₃ based materials that currently have the highest figure of merit.
Since it was as small as ^-3 / K and the efficiency was low, its practical application range was extremely limited.

[0005]

SUMMARY OF THE INVENTION The present invention provides thermal insulation between thermoelectric materials by spatially separating the current inflow and outflow portions of the thermoelectric material after passing a current and before the device reaches a steady state. The same thermoelectric material is used as a means for dramatically improving the efficiency of the heat pump device.

[0006]

When a current is applied to the basic components of the heat pump device shown in FIG. 4, the temperature inside the thermoelectric material changes with time as shown in FIG. When energization is continued for a sufficiently long time, the steady state of (d) is finally reached, and the temperature gradient in the thermoelectric material becomes constant. The maximum value of the efficiency in the steady state is determined by the material-specific Z, and therefore the same thermoelectric material cannot basically improve the efficiency. However, in the states of (a), (b), and (c) in FIG. 3, the Peltier heat generated in the current inflow portion remains near the inflow portion while being diffused by heat conduction, and the loss of Peltier heat due to heat conduction is small. It has not occurred. On the other hand, the cooling heat of the current outflow portion is in the same state. Therefore, for example, when the state of (c) is reached, the energization is stopped, the high temperature part and the low temperature part of the thermoelectric material are spatially separated, and both parts are thermally insulated. When each reaches a thermal equilibrium state, (e) become that way. In this way, heat loss due to heat conduction in the thermoelectric material can be significantly reduced, so that the efficiency of the heat pump device can be improved.

Further, if the heat loss due to heat conduction can be suppressed, the thermoelectric material can be made thinner by adjusting the time and current for energization, so that the heat loss due to Joule heat can be reduced and the efficiency can be further improved. Is.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of the most basic device portion according to the present invention, and shows its configuration. First, as a thermoelectric material on the heat absorption side, Bi ₂ Te ₃ —Sb ₂ Te ₃ was placed on the base 1.
A P-type semiconductor (thickness 3 mm) 2 made of an alloy was electrically connected to the copper plate 3 used as an electrode, and the heat exchange fins 4 were formed on the copper plate. In addition, the heat exchange efficiency was increased by the blower fan 5 provided on the base. Similarly, as a heat radiation side, a P-type semiconductor (thickness 3 m
m) 6, a copper plate 7, and a heat exchange fin 8 were configured. Further, by attaching the drive motor 9 to the base, the end surface 10 of the heat absorption side semiconductor and the end surface 11 of the heat dissipation side semiconductor are attached.
It was made easy to connect and disconnect. Further, a thermocouple 12 for temperature monitoring is electrically insulated from the P-type semiconductor in each P-type semiconductor.

First, the end face 10 and the end face 11 are added to this device.
A current of 10 A / cm ² was made to flow from the heat absorbing side semiconductor 2 to the heat radiating side semiconductor 6 in the state of connecting. Next, 1 second after the energization, the semiconductors on the heat absorbing side and the heat radiating side were separated from the end faces by the drive motor 9 to insulate each other. When the temperature of the atmosphere is set to 20 ° C, about 10 seconds after the separation, after reaching the thermal equilibrium state inside each semiconductor, the temperature is measured and the endothermic side semiconductor is 17.5 ° C and the heat radiating side semiconductor is 22.5 ° C. ℃, cooling efficiency (COP)
Was about 7.2. Furthermore, the electric current that flows is 100 A / c
m ² and pulsed for about 0.1 second, and when semiconductors were connected and disconnected at the same time, after reaching equilibrium, the endothermic semiconductor was 16.0 ° C. and the heat radiating semiconductor was 26.5 ° C. The efficiency at that time was about 20. This value is nearly ten times as large as that when the same thermoelectric semiconductor (Z = 2.5 × 10 ⁻³ / K) is used in the conventional steady state.
The separated heat absorbing side and heat radiating side semiconductors were sufficiently exchanged with the object to be cooled such as the atmosphere or the object to be heated by the heat exchange fins, and then repeatedly connected, energized and disconnected. In order to use the device of the present invention using such a pair of semiconductors as a heat pump for an air conditioner, for example, it was convenient to take out the cooling output sequentially with a configuration having a plurality of semiconductor pairs. As a result, a highly efficient heat pump having continuous cooling capacity or heating capacity could be obtained.

Bi ₂ Te ₃ -Sb used in this example
_{Since the 2} Te ₃ -based thermoelectric material has relatively high thermal conductivity and electric conductivity, it takes a short time to reach a steady state after energization. Therefore, to prevent heat loss due to heat conduction of Peltier heat,
Accurate control of energization and disconnection time is required, and a relatively thick thermoelectric material is desirable. Therefore, a device according to the present invention was prototyped using a ZnSb-based thermoelectric material having a lower thermal conductivity. It was possible to make a temperature difference of about 10 ° C. by disconnecting the device 2 seconds after energization, but the efficiency slightly decreased. It was also found that a large temperature difference can be obtained in a short time as the current density is increased. It was possible to optimally set the thickness of the thermoelectric material, the energization time, and the current density according to the physical properties of the thermoelectric material used in this way and the purpose of the heat pump.

In the embodiment of the present invention, an example in which the current inflow side and the outflow side of the thermoelectric material are thermally separated is shown as the most specific means. It is also conceivable to obtain a device with high efficiency by constructing a thermoelectric material whose conductivity changes between the heat absorbing side and the heat radiating side.

In the conventional heat pump device using the Peltier effect in the steady state, by alternately connecting P-type semiconductors and N-type semiconductors in series, the total amount of current required to drive the device is reduced, and at each contact. Endothermic,
It is configured to efficiently dissipate heat. Also in the present invention, the total amount of current is reduced by configuring the P-type semiconductor and the N-type semiconductor in series as shown in FIG.
The power terminals could be placed on the same side.

[0013]

INDUSTRIAL APPLICABILITY As described above, the heat pump device according to the present invention has a limited range of application of thermoelectric phenomenon because of its low performance index that exceeds the limit of efficiency conventionally determined by the performance index of the thermoelectric material used. It will expand dramatically.

[Brief description of drawings]

FIG. 1 is a basic configuration diagram of a heat pump device according to an embodiment of the present invention.

FIG. 2 is a block diagram of a heat pump device according to the present invention in which different total current amounts are reduced.

FIG. 3 is a diagram showing changes over time in the temperature distribution in the thermoelectric material.

FIG. 4 is a configuration diagram of a conventional heat pump device.

[Explanation of symbols]

 1 Base 2 P-type semiconductor (thickness 3 mm) 3 Copper plate 4 Heat exchange fin 5 Blower fan 6 P-type semiconductor (thickness 3 mm) 7 Copper plate 8 Heat exchange fin 9 Drive motor 10 End surface of heat absorption side 11 Heat dissipation side End face of semiconductor 12 Thermocouple 13 Metal plate 14 Metal plate 15 N-type semiconductor 16 P-type semiconductor 17 Heat exchanger

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koji Nakagiri 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (2)

[Claims] 1. A thermoelectric material having a Peltier effect, a means for passing an electric current through the thermoelectric material, and a means for insulating between a current inflow side and an outflow side of the thermoelectric material,
A heat pump device comprising an electric current supply means. 2. The means for insulating the thermoelectric material from the current inflow side and the current outflow side is to spatially separate the two parts.
The heat pump device described.