JPH01107073A - Cooling device - Google Patents

Abstract

PURPOSE: To provide a cooling apparatus capable of obtaining low temperature in a short time by defining equilibrium pressure upon hydrogen occulusion of first metal hydride to be lower than equilibrium pressure at low output temperature of second metal hydride. CONSTITUTION: First metal hydride 3 and second metal hydride having different hydrogen equilibrium pressure at an arbitrary temperature are put in containers 1, 2, which containers are then communicated with each other through a pipe 5 having a valve 6 in the course thereof and are filled with hydrogen gas to construct an intermittently operated cooling apparatus. Herein, temperature and heat capacity of the low equilibrium pressure first metal hydride 3 before hydrogen occulusion reaction, and heat capacity of the container 1 are defined such that the equilibrium pressure of the first metal hydride 3 upon hydrogen occulusion to be lower than the equilibrium pressure of the second metal hydride at cold output temperature. Hereby, temperature rise due to heating is suppressed to be lower, and hence low temperature is ensured in a short time.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention can be applied to air conditioning, refrigeration, freezing, etc. as a means of obtaining lower temperatures using thermal energy. be.

In particular, the present invention is an effective method when rapid cooling is required, and is useful as a rapid cooling aid in refrigerators and freezers.

Conventional technology When preserving foods by freezing, it is important to rapidly lower the temperature and freeze them in order to maintain freshness.
In a normal refrigeration system using a compression refrigerator, a method is used in which the temperature of the frozen object is lowered by bringing the object into direct contact with a refrigerant evaporator, but in order to cool it even more rapidly, It is necessary to further lower the evaporation temperature of the refrigerant. However, as the temperature decreases, the evaporation pressure also decreases, so in order to maintain the capacity, a compressor with a higher capacity is required, and during normal operation, the equipment becomes oversized and uneconomical.

Therefore, a method is to use an intermittent cooling system such as a metal hydride cooling system, which is activated only when rapid cooling is required, and is kept in a ready state by backflowing hydrogen gas during normal operation. It has been made clear.

This is considered a type of cold heat storage, and the combination of metal hydrides and hydrogen is a useful method because there are materials that have a sufficiently high equilibrium pressure even at low temperatures.

First, the principle of an intermittent cooling device using metal hydrides will be briefly explained.

As shown in Figure 2, an intermittent heat pump consists of two containers (1.2) filled with metal hydride alloys (3.4) that have different equilibrium pressures at the same temperature (temperature is arbitrary). A communicating piping 5 and a valve 6 are provided between them, and after evacuation, hydrogen gas is sealed.

FIG. 3 is a cycle diagram showing an intermittent cooling device.

The horizontal axis is the reciprocal of the feed temperature T, and the vertical axis is the logarithm of the pressure, and the temperature-pressure characteristics of each metal hydride are represented by - lines on this diagram.

Let us now assume that the characteristic line of a metal hydride with a low equilibrium pressure is represented by AD, and the higher equilibrium pressure is represented by Be, and the respective materials are represented by MHI, MH
I'll call it 2. MHL in container 1 in Figure 2, container 2
Assume that MH2 is contained in .

First, assume that MHL is in a relatively hydrogenated state and MH2 is in a relatively dehydrogenated state, and MHL is heated to 74 degrees.
If MH2 is kept at 72 degrees, each equilibrium pressure is Pj + P
2, and Pl>T2, by opening valve 6 in FIG. 2, hydrogen moves from container 1 to container 2, and M
Hl is dehydrogenated and MH2 is hydrogenated.

At this time, MH1 absorbs heat and MH2 generates heat, so it is necessary to heat MHL and radiate heat from MH2.

After a certain period of time, most of the hydrogen is transferred from MHL to MH2, so when valve 6 is closed and MHL is cooled to 74 degrees, its equilibrium pressure drops to T4. Next, when valve 6 is opened, MH
Since 2 is initially at a temperature of T2 and the pressure is also at T2, hydrogen is rapidly released from MH2 and adsorbed by M)11.

At this time, since MI(2) is an endothermic reaction, the temperature drops to T3 and continues to absorb heat at this temperature. In other words, cooling capacity is generated.

6 at Beno temperature is determined by the desorption rate of hydrogen due to the pressure difference p3-p4 and the magnitude of the heat flow into MH2.

Also, since MH1 generates heat, it is impossible to maintain the temperature T4 unless this heat is quickly removed, and as the temperature rises, the equilibrium pressure P4 also rises, T3-T4 decreases, and the reaction slows down. , cooling capacity is reduced.

Therefore, if the heat dissipation of MHL is sufficient, the endothermic reaction of MH2 will proceed rapidly, and the T2 temperature will be much lower than the initial T2 temperature.
3 Demonstrates cooling ability depending on the temperature.

This is a method of obtaining a low temperature based on the principle of an intermittent heat pump cycle, and suppressing the temperature rise of MHL is the key to rapidly achieving a lower temperature.

Since the materials used in the intermittent cycle are limited, the reaction will be completed in a certain amount of time, so when valve 6 is closed again and MHL is heated to T1, the pressure will rise to Pl.
When valve 6 is opened, hydrogen moves from MHL to MH2 again,
A-7 is now ready for the next cooling.

When trying to constantly cool a limited space such as a refrigerator using this principle, if a container filled with MH2 is fixed and installed in that space, it will become sticky and generate heat during regeneration. It is inconvenient to do so.

However, when used appropriately, the intermittent operation cooling device using metal hydrides can be is effective as a means of obtaining a low temperature in a short time.

Problems to be Solved by the Invention As mentioned earlier, when performing rapid cooling with an intermittent metal hydride cooling device, there is a possibility that the temperature obtained will be lower than that of a normal refrigeration cycle using R12, for example. ,
Since a temperature of -50° C. can be sufficiently obtained with TiTi-0r-based alloys, the question is whether the cooling rate is sufficiently fast.

It is well known that the reaction rate of this reaction system is temperature-determined, and in order to rapidly desorb hydrogen from metal hydride MH2, it is necessary to rapidly adsorb hydrogen to metal hydride MH1. It goes without saying that there is.

The reaction in which hydrogen is adsorbed on metal hydride MH1 is an exothermic reaction, so if this heat is not rapidly removed, the temperature of metal hydride MH1 will rise, pushing up the equilibrium pressure, which will lower the equilibrium pressure of metal hydride MH2. The difference between the

Therefore, improving the heat dissipation of metal hydride MH1 is an important issue in order to speed up the reaction rate and lower the temperature rapidly, but metal hydrides have the disadvantage of being finely powdered and having poor heat conductivity. However, it requires placing the metal hydride in a thin layer on a large heat transfer surface, which is difficult to implement.

A solution to the problem is to have different hydrogen equilibrium pressures at arbitrarily determined temperatures2.
Different types of metal hydrides are placed in containers, these containers are connected through piping with a valve in the middle, and filled with hydrogen gas to form an intermittent operating cooling device. The hydrogen equilibrium pressure at the temperature reached as a result of the first metal hydride MH1 absorbing hydrogen in a container without active heat dissipation means and generating heat is higher than that of the second metal with a high equilibrium pressure used on the cooling side. The second metal hydride Ml(2
As the pressure of the first metal hydride M becomes lower than the equilibrium pressure of
The temperature before the hydrogen storage reaction of H1 and the heat capacity of the first metal hydride MH1 and its container are determined.

The function as an intermittent cooling device has already been established and will not change in any way.

In the present invention, even if the first metal hydride MH1 is not provided with active heat dissipation means, the temperature rise is as follows.

The temperature at the start of the adsorption reaction of the first metal hydride MH1 is T
4. The temperature reached is T41 when there is no heat radiation.

The total heat capacity of the first metal hydride MH1 and its container is C1. If the heat 9hage generated during the reaction is Ql, then (T4/-T4)C,=Q.

Further, if the equilibrium pressure of the first metal hydride MH1 at F[+4/degrees] is P4', and the equilibrium pressure of the second metal hydride MH2 at the required cooling temperature is P3, then P4/<P3 holds true.

EXAMPLE An example of the present invention is shown below. As the first metal hydride, Tio, 5zro, 5Mno, 8Cr1. oCuo
, 2 is used. Tier as the second metal hydride,
2Mno,,Q is used. FIG. 1 shows temperature-pressure diagrams of these metal hydrides and cycles using them.

20ooy of the first metal hydride was used for 430f of the second metal hydride, and this was housed in a 25001 container.

The amount of hydrogen transferred in this system is approximately 2 moles.

The calorific value in the first metal hydride is 15 KO! Ll
Met.

The temperature T4 at the start of the reaction was O'C.

If the temperature rise width due to heat generation is ΔT, then 1o...-1 ΔT x heat capacity = 15Kcal, and the heat capacity is approximately 5o
oKcal/degree, the temperature increase width ΔT was 30°C2, so the temperature +r4/ after the completion of the reaction was 30°C.

The hydrogen equilibrium pressure at 30'C of the first metal hydride is o
s4kg/d, and -50'C of the second metal hydride
The hydrogen equilibrium pressure at was 0.7 kg/cA.

In this example, the amount of the first metal hydride is more than enough to adsorb and desorb 2 moles of hydrogen, so it is possible to mix cheaper metal powder into the metal hydride, and the weight ratio There was no problem even when copper powder was mixed at a ratio of 1:1.

In general, the coefficient of performance of a cooling cycle (cooling output ÷ heating input)
In order to make the heat capacity of the metal hydride as large as possible, it is important to minimize the heat capacity of the container for the metal hydride. It is important to have a wide range.

Therefore, as in the present invention, the first metal hydride or 1,
Increasing the heat capacity of the container that houses it 11 ノ・-
This requires extra energy for heating, which is disadvantageous in terms of coefficient of performance.

However, if the purpose is to cool as quickly as possible using this cooling cycle as in the present invention, increasing the heat capacity of the first metal hydride and its container will reduce the temperature increase due to heat generation. It is extremely effective to keep the temperature low and proceed with the rapid Hiko adsorption/desorption reaction, starting at the normal temperature of T4' or between T4 and T4', and discarding the heat from the reaction with a heat radiator. However, if you try to keep the temperature as low as possible, you will not be able to keep up with the rapid reaction, and the temperature of each metal hydride particle will rise sharply compared to the temperature of the radiator, slowing down the reaction rate. Significantly lower.

Effects of the Invention As described above, the cooling device using a metal hydride according to the present invention can be applied to a device that cools a limited amount of material in as short a time as possible, such as a quick freezing system added to a freezer. Extremely effective.

[Brief explanation of the drawing]

Figure 1 is a cycle diagram on a temperature-pressure diagram of an embodiment of the present invention, Figure 2 is a configuration diagram of an intermittent heat pump cycle, and Figure 3 is a diagram on a temperature-pressure diagram showing the principle of an intermittent heat pump cycle. It is a cycle diagram. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure Ir) 0 11) S) 40XI K) 10 0
-10-ffl -XI -41J -50 2nd f
! 1 Figure 3 TIT+T273 →Complete

Claims (1)

[Claims] Two types of metal hydrides with different hydrogen equilibrium pressures at arbitrarily determined temperatures are placed in containers, and these containers are communicated through a pipe with a valve in the middle, and hydrogen gas is filled to form an intermittent-operating cooling device. , the first metal hydride with a low equilibrium pressure absorbs hydrogen in a container without active heat dissipation means, and as a result of generating heat, the equilibrium pressure at the temperature reached becomes that of the second metal hydride with a high equilibrium pressure. the temperature of the first metal hydride before the hydrogen storage reaction, and
A cooling device characterized in that it defines the heat capacity of a first metal hydride and its container.