JP3164130B2 - Heat exchanger for equipment with regenerator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The claimed invention is a Stirling engine and the Stirling refrigerator, the regenerator, such as Gifford-McMahon refrigerator (thermal storage unit, 蓄 chiller) using equipment with, that is, the Stirling engine machinery, equipment (Automobiles, heat pumps, etc.), Stirling refrigerators, GM
Refrigerator application equipment (cryopump, Riniaka for) using 蓄 chiller such as the refrigerator freezer, it relates in regenerator across the heat exchanger of the cooling device) of the superconducting device.

[0002]

2. Description of the Related Art Stirling engines, Stirling refrigerating machines, and the like are typical examples of machines that perform heat transport or work amplification (generation) by reciprocating fluid using a regenerator. In the regenerators of these machines, heat exchangers are used at both ends to always transfer heat to and from the outside. For example, a configuration diagram of an SAE technical paper series engine is shown in FIG. Numerals 1 and 6 are called a compression piston and an expansion piston, respectively, and cause pressure fluctuation and fluid movement in the system. 2 and 3 are the heat exchangers we want to consider here. Reference numeral 2 denotes a low-temperature side heat exchanger that performs heat radiation with cooling water from the outside. Reference numeral 3 denotes a high-temperature side heat exchanger, which is a portion for taking in heat from the outside. In the example of this figure, heating is performed by a fire. Thermal storage unit, i.e. the high temperature side and the low temperature (room temperature) portion is connected by a regenerator 4, amplification work among the thermal storage unit, the heat transport takes place. A device with such a regenerator functions only when heat enters and exits the regenerator. Most of the structure of the heat exchanger is such that a working fluid flows through a fine flow path 7 or 8 as shown in 2 or 3 in FIG. 1. A heating source 5 or a cooling source (such as cooling water) is provided outside the flow path. It comes into contact.

[0003] Considering this heat exchanger in thermoacoustic theory, it is as follows. It is assumed that the heat exchanger is considered as a bundle of flow passages having a certain diameter, and the internal fluid is heated or radiated from the internal fluid at a constant heating / radiation density from the flow channel wall. now,
As an example, consider the case of a Stirling engine. In the engine, the high temperature side of the regenerator is the heating side, and the low temperature side is the heat radiation side. The heat supplied from the heat exchanger on the high temperature side is carried to the regenerator and used for generating work in the regenerator. The transport of heat to the regenerator in this heat exchanger is important and problematic. If heat is supplied to the fluid at a uniform density from the walls of the flow path of the high-temperature heat exchanger, the heat is transferred to the regenerator in order for the heat to be carried through the flow path toward the regenerator. As we get closer, the heat flux must gradually increase. Incidentally, as a conclusion obtained from the thermoacoustic theory, it is shown that the heat flux Q carried by a vibrating (reciprocating) fluid is the sum of three heat fluxes obtained by the following Expressions 1, 2, 3, and 4. I have.

[0004]

(Equation 1)

[0005]

(Equation 2)

[0006]

(Equation 3)

[0007]

(Equation 4)

Here, the meanings of the symbols in the above mathematical expressions are as follows. Qprog: Heat flux carried by traveling wave component Qstand: Standing wave component QD: Heat flux carried only by positional displacement of fluid Fs: Amount related to heat capacity of channel wall of heat exchanger χ ': Reversible change Degree χ ″: Degree of irreversible change ω: Angular frequency of vibration β: Coefficient of thermal expansion Tm: Average temperature of working fluid ρm: Average density of working fluid Cp: Specific heat of working fluid ▽ Tm: Temperature gradient of channel wall ξ ₀ , Prog: Traveling wave component of displacement amplitude _{０ 0} , stand ² : Standing wave component of displacement amplitude

[0009] Since Qprog and Qstand are independent of the sound gradient of the flow path and are determined by the frequency of vibration, the size of the flow path, and the like, there is no significant displacement along the flow path. On the other hand, since the QD is an amount proportional to the temperature gradient, the magnitude of the QD may change when the magnitude of the temperature gradient changes. In order for the heat flux to increase as one approaches the regenerator along the heat exchanger, Qpr
ong, Qstand cannot be changed, so we have to rely on the remaining QD. That is, the temperature gradient changes along the flow path of the heat exchanger, and as a result, the QD changes along the heat exchanger, so that it is possible to cope with uniform heat supply from the flow path wall.
At that time, the distribution of the temperature gradient, that is, the temperature distribution along the fluid of the heat exchanger, is such that the QD is proportional to the temperature gradient, and the QD increases uniformly along the flow path. It is easily required that a parabolic change must be made. That is, in a heat exchanger having a flow path having a uniform diameter, in order for heat to flow in and out uniformly from the flow path wall, a parabolic temperature distribution is inevitable along the flow path.
FIG. 2 shows such a temperature distribution. FIG. 2A shows the case of an engine, and FIG. 2B shows the case of a refrigerator. If there is a temperature gradient as shown in this figure, the following problem occurs. Considering the case of an engine,
As shown in (a), there is a substantially uniform temperature gradient in the regenerator (heat accumulator), but the heat exchangers at both ends have a parabolic temperature distribution as shown in FIG. Point temperature (T
A), the cooling temperature is the temperature at point D (TD), but the temperature difference between both ends of the regenerator is TB-TC. The output and efficiency of the Stirling engine are higher as the temperature difference between both ends of the regenerator is larger, and the heating source is TA and the cooling source is TD. Therefore, ideally, a temperature difference of TA-TD is expected.

Similarly, a regenerator for a refrigerator is shown in FIG.
As shown in (b), the heat exchangers on the high temperature side and the low temperature side each draw a parabolic temperature distribution curve opposite to that of the engine as shown in the figure. It is easily understood that this temperature distribution is also disadvantageous for the refrigerator. That is, the regenerator high-temperature end (the temperature at the point B ', TB') is higher than the heat radiation temperature on the high temperature side (the temperature at the point A ', TA'), and the refrigeration generation temperature (D ', the temperature at the low temperature part). The temperature at the point TD ') is higher than the regenerator low end temperature (the temperature at the point C' and TC '), resulting in an unnecessary temperature gradient in the regenerator, resulting in reduced efficiency. It has become.

It is an essential problem associated with the conventional heat exchanger having a uniform cross-sectional area of the flow passage that the useless temperature distribution is generated at both ends of the regenerator as described above. This was a major cause of lower efficiency.

[0012]

The problem to be solved by the invention of claim 1 of the present application is to eliminate the unnecessary temperature distribution in the heat exchanger.

Another object of the present invention is to provide a practical configuration for solving the above-mentioned problems.

[0014]

According to the first aspect of the present invention, a regenerator such as a Stirling engine, a Stirling refrigerator or a Gifford McMahon refrigerator is provided .
High temperature side heat exchanger and low temperature at both ends of the regenerator
The heat exchanger to which the side heat exchanger is connected,
The working fluid flow path inside the warm side heat exchanger is close to the regenerator.
As the flow path size decreases, the low-temperature side heat exchanger
As the working fluid flow path inside the
Machine with regenerator characterized by reduced flow channel size
It is a heat exchanger of the vessel .

Further, in the invention of claim 2 of this application , a large number of wire meshes or perforated plates are packed in the flow path of the working fluid.
Flow path by embedding and sequentially changing their fineness
2. The method according to claim 1, wherein the dimensions are changed stepwise.
It is a heat exchanger for equipment with a regenerator .

[0016]

As described above, the role of the heat exchanger is to transfer heat to and from the outside world and to transport the heat to the regenerator. The transport amount (heat flux) also needs to increase as it goes downstream, and the change in the heat flux size is realized by applying a temperature gradient in a form that depends on the temperature gradient dependence of QD. However, in order to provide a heat flux distribution without a temperature gradient, it is necessary to apply a heat flux distribution other than the QD. The candidates are Qprog and Qstand, and if they do not have a distribution depending on the position, distributions are given to χ ′ and χ ″ as can be understood from the respective mathematical expressions 2 and 3. 3, is a function of ωτ, ω is the operating angular frequency of the refrigerator, and τ is the heat relaxation time between the fluid and the heat exchange wall defined by the following equation (5).

[0017]

(Equation 5)

In the above equation (5), r ₀ is a representative length of the flow path,
(Radius for circular tubes, half the spacing for parallel plates),
α is the temperature spread coefficient of the fluid, and is a constant if the temperature is constant. In order to generate a distribution in χ ′ and χ ″ without a temperature distribution, it is the remaining method to provide a distribution to r _0. The invention according to claim 1 is based on the dimensions of the flow path of the heat exchanger (representative length, etc.). ) And Qprog, Qs
The heat flux distribution can be realized without the temperature distribution due to the position dependence of tan.

According to the second aspect of the present invention, a heat exchanger having a practical configuration can be obtained.

[0020]

FIG. 4 shows a specific embodiment, that is, an example of a Stirling engine. Since it is effective for a three-way engine to have a relatively large traveling wave component and to rely on Qprog,
It is desirable to increase χ ′ in the direction in which the heat flux increases. That is, the representative length of the flow path decreases along the direction of the heat flux. This is because, as shown in FIG. 4, the dimension (diameter and the like) of the flow path 8 ′ becomes smaller as it approaches the regenerator 4 in the high-temperature side heat exchanger 3, and the flow path increases as it approaches the regenerator 4 even in the low-temperature side heat exchanger 2. The size of 7 'is reduced. Since it is practically difficult to continuously change the diameter and gap of the flow channel, a wire mesh is packed in a fixed size flow channel 7 "in the heat exchanger as shown in FIG. A, B,
A similar effect can be obtained by a method of gradually changing the position gradually in the order of C, D, and E steps. These methods are basically the same for an engine and a refrigerator. However, the amount of heat entering and exiting the heat exchanger and the temperature differ depending on the engine and refrigerator, and the difference in capacity.Therefore, it is necessary to determine the way to change the flow path size or the distribution of the wire mesh according to the difference. is there.

[0021]

As described above, according to the first aspect of the present invention, the operation of the heat exchanger is changed by changing Qprog according to the change in the amount of heat transported by the working fluid in the heat exchanger. Eliminating the temperature gradient along the flow path of the fluid can increase the efficiency of the device as a heat engine. According to the second aspect of the present invention, a heat exchanger having a practical configuration can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a Stirling engine provided with a conventional heat exchanger.

[Figure 2] a heat exchanger and a regenerator (thermal storage unit, 蓄 chiller) is a diagram showing the temperature distribution over, (a) shows the case of a Stirling engine,畜冷refrigeration such as (b) Stirling refrigerator Each case is shown.

FIG. 3 is a diagram showing the dependence of χ ′ and χ ″ on ωτ (when the flow path is a circular pipe).

FIG. 4 is a diagram showing an embodiment of the invention of this application.

FIG. 5 is a diagram showing a detailed configuration of a heat exchanger in FIG.

[Explanation of symbols]

1 compression piston 2 the low-temperature heat exchanger 3 high temperature heat exchanger 4 regenerator (thermal storage unit) 5 heating source 6 hydraulic fluid channel of the expansion piston 7 low temperature heat exchanger of the hydraulic fluid channel 7 'in the low temperature heat exchanger 7 "Working fluid flow path in low temperature heat exchanger 8 Working fluid flow path in high temperature heat exchanger

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F28F 13/06 F25B 9/00 F25B 9/14

Claims (2)

(57) [Claims] 1. A Stirling engine or a Stirling refrigerator, a playback device such as a Gifford-McMahon refrigerator lifting
High temperature side heat exchanger and low temperature at both ends of the regenerator
The heat exchanger to which the side heat exchanger is connected,
The working fluid flow path inside the warm side heat exchanger is close to the regenerator.
As the flow path size decreases, the low-temperature side heat exchanger
As the working fluid flow path inside the
Machine with regenerator characterized by reduced flow channel size
Vessel heat exchanger . 2. A method according to claim, characterized in that the flow channel size is changed stepwise by successively changing the flow path into a number of wire mesh or perforated stuffing plate and fineness of their eyes of the working fluid 1 Heat exchanger for equipment with regenerator as described .