JP2009008334A - Heat transfer medium, and heat transfer device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat transfer medium for solving a problem of CO<SB>2</SB>having excellent characteristics as a heat transfer medium, and to provide a heat transfer device which uses the heat transfer medium which serves as a secondary heat transfer medium, or is used for a natural circulation type heat pump cycle which operates at a low pressure, exhibits a favorable coefficient of performance, and is convenient in use. <P>SOLUTION: The heat transfer device uses the heat transfer medium c mainly containing CO<SB>2</SB>as the heat transfer medium for heat transfer equipment 1 for cooling or heating. The heat transfer medium c formed by adding dimethyl ether in a molar ratio of 1-50% to CO<SB>2</SB>is used as the secondary heat transfer medium r<SB>2</SB>interposed between a heat exchanger of a primary heat pump cycle and a heat load, for transferring heat between the primary heat pump cycle and a heat load. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to a heat transfer medium comprising, as a main component, CO ₂ that is frequently used in a heat transfer facility such as a refrigeration facility or a heat pump, and dimethyl ether added to CO ₂ as a natural heat transfer medium that does not cause global environmental pollution. And a heat transfer device using the same.

In order to prevent global environmental pollution, in particular, ozone layer destruction and global warming prevention, the heat medium used in refrigeration equipment or heat pump equipment is being converted from a fluorocarbon heat medium to a natural heat medium. In particular, CO ₂ is much less harmful than fluorocarbon, non-flammable, non-toxic, safe and inexpensive, and therefore tends to be frequently used as one of the natural heat media that exist in nature.

Since CO ₂ has a large sensible heat effect and easily enters a supercritical state on the high pressure side of the cycle, a high coefficient of performance can be obtained, and hot water supply at a maximum of about 90 ° C. is possible. Therefore, in recent years, it has been widely used as a refrigerant for heat pump water heaters with the name of Ecocute for heating and hot water supply.

In addition, CO ₂ has a low liquid viscosity of 64.5 × 10 ⁻⁶ Pa · S (298 K), excellent fluidity, and low transportation power. Therefore, the heat transfer medium is used as a natural circulation type heat transfer medium in which the heat transfer medium is circulated by a temperature difference and a liquid head difference without using a physical forced circulation device that involves compression or lifting of the heat transfer medium.

However, CO ₂ has a low boiling point (−78.5 ° C.) and a high critical pressure (7.34 MPa), and the operating pressure in the refrigeration cycle or heat pump cycle of the CO ₂ refrigerant is 10 MPa, which is much higher than that of other refrigerants. For this reason, there is a problem in that the cost of manufacturing the apparatus is high because each component of the system equipment must be made to have an ultra-high pressure specification. Further, CO ₂ has a critical temperature of 31 ° C., and needs to be 31 ° C. or lower in order to liquefy the high-pressure gas phase CO ₂ refrigerant.

In summer, the outside air temperature frequently exceeds 31 ° C. Under such conditions of the outside air temperature, the CO ₂ refrigerant does not liquefy (condense) in the condenser, so that heat cannot be released by condensation. For this reason, a special cooling means for previously cooling the fluid to be cooled such as water or air used in the CO ₂ gas cooler is used, or a non-condensing cycle (supercritical cycle) is caused, and the coefficient of performance is lowered.

Applicants have has previously based on the total moles of dimethyl ether and CO _2, dimethyl ether 10 to 80 mol%, proposes a hot water / heating refrigerant compositions containing CO ₂ 90 to 20 mol% (Patent Document 1). The present invention achieves high thermal efficiency by mixing both CO ₂ well dissolved in dimethyl ether and having a high heat transfer effect in physical properties, and the critical temperature of dimethyl ether is 126.9 ° C. and the boiling point is − Focusing on the significant difference between 78.5 ° C. and CO ₂ , the present inventors have found a hot water / heating refrigerant having an excellent coefficient of performance that operates at low pressure.

The present applicants have previously proposed, based on the total moles of dimethyl ether and CO _2, dimethyl ether 1-10 mol%, the hot water / heating refrigerant compositions containing CO ₂ 99 to 90 mol% (Patent Document 2). In the present invention, when the content of dimethyl ether is 10 mol% or less, the refrigerant composition is made nonflammable, and when a particularly high safety standard is required, for example, a refrigerant filling portion exists in a living room. A hot water supply / heating refrigerant suitable for use in a direct leakage system or in a sealed place such as a room is realized.

JP 2006-22305 A JP 2007-91772 A

  However, the fluid used for the secondary heat transfer medium that is interposed between the heat exchanger of the primary heat pump cycle and the heat load and transfers heat between the primary heat pump cycle and the heat load has a low viscosity. It requires good fluidity, high specific heat, high sensible heat efficiency, and inert and stable physical properties. On the other hand, as the secondary heat transfer medium such as brine becomes higher in pressure or lower in temperature, the viscosity increases and the flow power load increases. Combustible materials have limitations such as safety.

CO ₂ has low viscosity, good fluidity, high specific heat, high sensible heat efficiency, and inert and stable physical properties, while the operating pressure of CO ₂ is very high and the condensation temperature is low For this reason, there is a problem that a special cooling means for precooling the fluid to be cooled such as water or air used in the CO ₂ gas cooler is used, or a non-condensing cycle (supercritical cycle) is performed, and the coefficient of performance is lowered. is there.
The same problem occurs even when CO ₂ is used in a natural circulation heat pump cycle.

  The hot water / heating refrigerant composition disclosed in Patent Document 1 or Patent Document 2 relates to a primary refrigerant applied to a primary heat pump cycle, and is applied to a secondary heat transfer medium or a natural circulation heat pump cycle. Not intended.

In view of the problems of the prior art, the present invention realizes a heat transfer medium that solves the above-described problems of CO ₂ having excellent properties as a heat transfer medium, and uses the heat transfer medium as a secondary heat transfer medium. Alternatively, an object of the present invention is to realize a heat transfer device that is used in a natural circulation type heat pump cycle, operates at a low pressure, has a good coefficient of performance, and is convenient.

In order to achieve this object, the heat transfer device according to the first aspect of the present invention provides:
In a heat transfer device using a heat transfer medium mainly composed of CO ₂ as a heat transfer medium in a heat transfer facility for cooling or heating purposes,
A heat transfer medium obtained by adding 1 to 50%, preferably 7 to 50%, of dimethyl ether in a molar ratio to CO ₂ is interposed between the heat exchanger of the primary heat pump cycle and the heat load, and the primary heat pump cycle. It is used as a secondary heat transfer medium that conducts heat between the heat load and the heat load.

In addition, the heat transfer medium of the first invention is
In a heat transfer medium mainly composed of CO ₂ used as a heat transfer medium in a heat transfer facility for cooling or heating purposes,
A heat transfer medium obtained by adding 1 to 50%, preferably 7 to 50%, of dimethyl ether in a molar ratio to CO ₂ is interposed between the heat exchanger and the heat load of the primary heat pump cycle, and the primary heat pump cycle. It is used as a secondary heat transfer medium of a heat pump cycle that performs heat transfer between a heat load and a heat load.

A heat transfer device (such as a refrigeration device or a heat pump device) of the first invention uses the heat transfer medium of the first invention having the above-described configuration as a secondary heat transfer medium. As mentioned above, dimethyl ether has a high critical pressure than CO _2, a first heat transfer medium of the present invention, the CO ₂ as the main medium, it by the addition of dimethyl ether, heat transfer only CO ₂ Since the condensation temperature is higher than in the case of the medium, condensation is possible by heat exchange with water and air at room temperature.
Thereby, the heat transfer device of the first aspect of the present invention does not require a special cooling means for condensing the heat transfer medium, and the convenience is greatly improved. Preferably, when dimethyl ether is added in an amount of 7 mol% or more, the effect of adding dimethyl ether is remarkably exhibited.

Further, in comparison with the heat transfer medium of only CO _2, the heat transfer medium of the first aspect of the present invention increases the amount of heat held per unit amount by the addition of dimethyl ether in the high temperature range, and thereby the heat transfer amount is also increased. To increase. For this reason, in the forced circulation type heat transfer device, the heat transfer efficiency is improved. The liquid thermal conductivity of dimethyl ether is 1453 × 10 ⁻⁴ W / mK (298 K), which is larger than the liquid thermal conductivity of CO ₂ 767 × 10 ⁻⁴ W / mK (298 K). For this reason, when dimethyl ether is added, the liquid thermal conductivity increases, so the heat transfer efficiency is improved in the supercritical region, and the evaporation heat transfer efficiency in the low temperature region is not lowered. For this reason, heat exchange efficiency is improved in a heat transfer device having a natural circulation heat pump cycle.

Addition of dimethyl ether to CO ₂ makes it flammable. When the molar ratio of dimethyl ether added to CO ₂ is 1 to 12%, it is a non-combustible region, when it exceeds 12 mol%, when it is up to 50 mol%, it becomes a slightly flammable region, and when it exceeds 50 mol%, it is a combustible region. It becomes. Therefore, in the heat transfer medium of the first aspect of the invention, the amount of dimethyl ether added is 1 to 50 mol% to make it nonflammable or slightly flammable, thereby ensuring safety in use.

The heat transfer device of the second invention is
In a heat transfer device using a heat transfer medium mainly composed of CO ₂ as a heat transfer medium in a heat transfer facility for cooling or heating purposes,
The heat transfer facility includes a natural circulation heat pump cycle that circulates the heat transfer medium by a temperature difference and a liquid head difference without interposing a physical forced circulation device with compression or lifting action of the heat transfer medium,
A heat transfer medium obtained by adding 1 to 35%, preferably 7 to 35%, of dimethyl ether in a molar ratio to CO ₂ is used in the heat pump cycle.

Further, the heat transfer medium of the second invention is
In a heat transfer medium mainly composed of CO ₂ used as a heat transfer medium in a heat transfer facility for cooling or heating purposes,
A heat transfer medium obtained by adding 1 to 35%, preferably 7 to 35%, of dimethyl ether in a molar ratio to CO ₂ is used as a heat transfer medium of a natural circulation type heat pump cycle.

The heat transfer device of the second aspect of the present invention uses the heat transfer medium of the second aspect of the present invention having the above-described configuration for a natural circulation type heat pump cycle (including a loop heat pipe or a heat transfer facility).
As shown in FIG. 1 described later, when dimethyl ether is added to CO ₂ , the critical temperature increases, and the critical temperature increases as the amount of dimethyl ether added increases. Therefore, the addition of dimethyl ether increases the evaporation temperature compared to the case of a CO ₂ only heat transfer medium. Therefore, since the condensation temperature than when only CO ₂ is increased, cold water, it is possible to condense by heat exchange with air. As a result, the heat transfer device according to the second aspect of the present invention eliminates the need for special cooling means for condensing the heat transfer medium, and greatly improves convenience.

As the amount of dimethyl ether added increases, the viscosity increases and the flow resistance increases. On the other hand, the gas specific gravity increases and the ascending force decreases. In natural circulation, circulation force is applied by the liquid head of the heat transfer medium condensed on the downstream side of the condenser and the ascending force of the heat transfer medium evaporated by the evaporator. However, as the amount of dimethyl ether added increases, the ascending force decreases. As a result, an area where the circulation performance of the heat transfer medium deteriorates appears.
In the heat transfer medium of the second aspect of the present invention, the flow resistance enabling natural circulation can be maintained by setting the amount of dimethyl ether added to CO ₂ to 1 to 35 mol%, preferably 7 to 35 mol%. it can.

Even if dimethyl ether is added to CO ₂ , if the heat transfer medium is in a liquid state, there is almost no difference in specific gravity, and therefore there is no difference in liquid head, but the viscosity increases, so the flow resistance increases. On the other hand, when the heat transfer medium is gaseous, the viscosity increases and the specific weight increases with the addition of dimethyl ether. Therefore, the ascending force of the gasified heat transfer medium is reduced.

If the amount of dimethyl ether added to CO2 is ₁ to 35 mol%, natural circulation can be formed in the heat pump cycle. Since the heat transfer amount (heat density) of the gaseous heat transfer medium is high, the heat transfer efficiency is increased if the amount of dimethyl ether added to form a natural circulation is in the range of 1 to 35 mol%.

In the heat transfer device of the second aspect of the present invention or the heat transfer medium of the second aspect of the present invention, when used in a heat transfer device installed indoors or in a closed space, the use in a combustible area is high in danger, 1-12 mol% the amount of dimethyl ether with respect to CO ₂ in mol%, preferably to a 7-12 mol%.

  In the heat transfer device according to the second aspect of the present invention, an auxiliary pump for assisting circulation of the heat transfer medium may be interposed in the heat transfer medium circulation path of the heat pump cycle. With this configuration, even when the circulation force of the heat transfer medium is insufficient, natural circulation can be reliably formed.

According to the heat transfer device of the first present invention, 1% to 50% dimethyl ether at a molar ratio to CO _2, preferably, 7-50% added heat exchangers and one heat transfer medium comprising primary heat pump cycle and the heat By using as a secondary heat transfer medium interposed between the primary heat pump cycle and the heat load interposed between the load and the heat transfer medium according to the second aspect of the present invention, ₂ is used as a secondary heat transfer medium in the primary heat pump cycle, in which dimethyl ether is added in a molar ratio to 1 to 50%, preferably 7 to 50%, compared with a heat transfer medium of CO ₂ alone. Condensation temperature rises and it becomes possible to condense by heat exchange with normal temperature water or air. This eliminates the need for special cooling means for condensation, and greatly improves convenience.

In addition, the addition of dimethyl ether to CO ₂ increases the amount of heat held per unit amount mainly in the high temperature range as compared with a heat transfer medium of only CO ₂ , so in the case of forced circulation type refrigeration equipment or heat pump equipment. The heat transfer efficiency is improved, and in the case of the natural circulation type, the heat exchange efficiency is improved.

Further, according to the heat transfer device of the second aspect of the present invention, the heat transfer medium is naturally circulated by the temperature difference and the liquid head difference without using a physical forced circulation device that involves compression or lifting action of the heat transfer medium. A heat transfer medium provided with a circulation type heat pump cycle, in which dimethyl ether is added to CO ₂ at a molar ratio of 1 to 35%, preferably 7 to 35%, is used for the heat pump cycle. According to the heat transfer medium of the present invention, a heat transfer medium obtained by adding 1 to 35%, preferably 7 to 35%, of dimethyl ether in a molar ratio to CO ₂ is used as a heat transfer medium for a natural circulation heat pump cycle. Therefore, the condensation temperature rises compared to a heat transfer medium of only CO ₂ , and condensation is possible by heat exchange with normal temperature water or air. This eliminates the need for special cooling means for condensation, and greatly improves convenience.

Moreover, since the gaseous heat transfer medium can increase the heat retention (heat density) within the range of the amount of dimethyl ether that can form a natural circulation, the heat transfer efficiency is increased.
[Example]

Experimental data relating to the physical properties of a heat transfer medium consisting only of CO ₂ and a heat transfer medium obtained by adding dimethyl ether to CO ₂ will be described.
FIG. 1 shows the results of testing the increase in critical temperature of a heat transfer medium consisting only of CO ₂ and a heat transfer medium in which dimethyl ether is added to CO ₂ . As shown in FIG. 1, it can be seen that the critical temperature increases as the amount of dimethyl ether added to CO ₂ increases. Therefore, if the critical temperature rises, the condensation temperature also rises, so that condensation easily occurs.

Even if the amount of dimethyl ether added to CO ₂ increases, the critical pressure does not decrease so much, but the saturation pressure decreases. Therefore, since the operating pressure of the heat transfer medium can be reduced, the pressure strength of each device constituting the heat pump cycle in which the heat transfer medium circulates can be reduced, thereby reducing the device manufacturing cost.

Next, FIG. 2 shows a comparison of physical properties and heat retention of a heat transfer medium containing only CO _{2 and} a heat transfer medium obtained by adding dimethyl ether to CO ₂ . As shown in FIG. 2, the specific gravity and specific heat increase as the amount of dimethyl ether added to CO ₂ increases, but the viscosity also increases. Enthalpy does not change in the difference from the liquid. Accordingly, when dimethyl ether is added to CO ₂ , the heat transfer efficiency is increased by the addition of dimethyl ether if the flow resistance due to the increase in viscosity remains within a range where natural circulation of the heat pump cycle is possible.

Next, FIG. 3, the heat pump device indicates (natural circulation) results of experiments performed using the heat transfer with the addition of dimethyl ether to heat transfer medium and CO ₂ CO ₂ alone using the solar heating apparatus as an evaporator The heat collection temperature and heat collection amount of the medium are shown. FIG. 3 shows that the heat collection temperature increases as the amount of dimethyl ether added increases even if the amount of heat transfer medium circulating in the heat pump cycle is the same. This seems to be because when dimethyl ether was added, the amount of heat retained per unit amount increased, thereby increasing the amount of heat transfer and improving the heat exchanger efficiency.

FIG. 4 shows the heat transfer test results of the evaporator in the low temperature region of the evaporator. That is, with an evaporator, heat transfer tubes are arranged vertically or horizontally, an evaporation test is performed with natural ventilation at an outside air temperature of 23.5 to 25.3 ° C, and from the start of evaporation (distance of heat transfer tube 0 m) to the end of evaporation The tube wall temperature (corresponding to the heat medium temperature) up to (heat transfer tube distance 5 m) is measured. As the heat transfer medium to be tested, one having only CO ₂ and one having 15% dimethyl ether added in molar ratio to CO ₂ were used.

From FIG. 4, it can be seen that the heat transfer efficiency at the time of evaporation of the heat medium in the low temperature region is substantially the same because both are at substantially the same temperature at the end of evaporation (heat transfer tube distance 5 m). In the case of only CO ₂ , the sensible heat exchange area and the latent heat exchange area clearly appear, whereas when dimethyl ether is added to CO ₂ , there is a temperature slip, and there is a sensible heat area and a latent heat area. You can see that there is no difference. Thus, it can be seen from FIG. 4 that when dimethyl ether is added to CO ₂ , the temperature rise gradient is constant, so that continuous and precise temperature control with respect to the load is possible.

Figure 5 shows a combustion of cases of the addition of dimethyl ether and CO ₂ If only CO _2, or dimethyl ether alone. It can be seen that the heat transfer medium when the amount of dimethyl ether added to CO ₂ is 12 to 50 mol% exhibits nonflammability or weak flame retardancy.

FIG. 6 shows the result of simulating the viscous resistance of the heat transfer medium at temperatures of 95 ° C. and 24 ° C. when natural circulation is performed at a pressure of 10 MPa in the circulation path of the heat transfer medium. 6, as compared with the case of the heat transfer medium only CO _2, towards the heat transfer medium with the addition of dimethyl ether to CO ₂ is increased viscous resistance, and as the amount of dimethyl ether increases, the viscosity resistance is increased I understand that.

Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the component parts described in this embodiment are not intended to limit the scope of the present invention to that unless otherwise specified.
[Embodiment 1]

Next, a first embodiment of the present invention will be described with reference to FIG. FIG. 7 is a system diagram showing a natural circulation heating device or a local heat radiating device 1 using the heat transfer medium of the present invention. In FIG. 7, a circulation path 2 through which a heat medium c in which 7 to 35% of dimethyl ether is added at a molar ratio to CO ₂ flows is provided, and an evaporator 3 and a heat recovery unit 4 are interposed in the circulation path 2. . The evaporator 3 is provided with a heat transfer pipe 5 connected to the circulation path 2 through which the heat medium c flows. The outside air a is taken into the evaporator 3 to introduce the heat, and the heat medium c is evaporated by the heat. . And the heat medium c will be in a supercritical state in the exit side of the evaporator 2. FIG.

  In the heat recovery unit 4, the heat transfer pipe 6 connected to the circulation path 2 is arranged in the air conditioning target space r, and the air conditioning target space r is heated with the heat of the heat medium c flowing through the heat transfer pipe 6, or local heat is generated. It collects in the evaporator 3 and dissipates heat in the heat recovery unit 4. And it condenses on the exit side of the heat recovery unit 4. The circulation path 2c on the outlet side of the heat recovery unit 4 is arranged with a height difference downward toward the outlet side so that a liquid head can be formed with the heat medium c condensed and liquefied. A natural circulation of the heat medium c is formed by the temperature difference between the liquid head H, the heat medium c downstream of the evaporator 3 and the heat recovery part 3 downstream, that is, the rising force of the heat medium c evaporated in the heat transfer pipe 5. The

In this embodiment, the heat medium c in which 1 to 35% of dimethyl ether is added to CO ₂ at a molar ratio is used. Therefore, as shown in Examples 1 and 2 of FIG. Since the temperature rises, the heat recovery section 4 can condense the heat medium c by heat exchange with normal temperature water or air without using any special cooling means, and convenience can be improved. Further, as shown in Example 2, 4 or 5 of FIG. 2, the specific heat of the heat medium c is larger than that in the case of only CO _2, so that the amount of heat held per unit amount is increased, thereby causing heat transfer. The amount also increases. Therefore, the heat exchange efficiency is improved.

Moreover, as shown in the experimental data of FIG. 4, since the temperature rise gradient in the heat transfer tube 5 of the evaporator 3 is constant, continuous and precise temperature control with respect to the load is possible. Further, as shown in Example 3 or 4 of FIG. 5, the heat medium c is incombustible or weakly flammable, so it is safe, and as shown in Example 2, 4 or 5 of FIG. Since it does not increase so much, a natural circulation can be formed.
[Embodiment 2]

Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 8 shows a solar heat collecting apparatus 10. In the figure, a heat medium c made of CO ₂ and dimethyl ether and having the same amount of dimethyl ether added as in the first embodiment flows through the heat medium circulation path 11. . In the circulation path 11, a heat collector 12 for collecting solar heat and a heat exchanger 13 for collecting solar heat collected by the heat collector 12 are interposed. The heat collector 12 and the heat exchanger 13 are installed at substantially the same height. A difference in height is provided between the inlet side and the outlet side of the heat collector 12 interposed in the circulation path 11, and a heat collecting pipe (not shown) disposed in the heat collector 12 has a lower inlet side in the vertical direction, It is arranged with an inclination so that the side becomes higher.

  Further, the heat exchanger 13 is provided with a heat transfer pipe 14 connected to the circulation flow path 11, and a heat recovery fluid f is supplied from a supply pipe 15 connected to the lower part of the heat exchanger 13. Heat is recovered from the heat medium by performing indirect heat exchange with the heat medium flowing through the heat transfer tube 14 and then discharged from the return pipe 16 connected to the upper portion of the heat exchanger 13. The outlet-side circulation flow path 11c of the heat exchanger 13 is arranged in the vertical direction so that the heat medium liquefied by heat exchange with the heat recovery fluid f in the heat exchanger 13 forms the liquid head H. .

The heat medium c naturally circulates in the circulation path 11 by the rising force of the heat medium c evaporated by the liquid head H and the heat collector 12. In the present embodiment, the operation and effect obtained by using a heat medium composed of CO ₂ and dimethyl ether as the heat medium c flowing in the circulation path 11 is the same as that in the first embodiment. In addition, as shown in Example 2 or 4 in FIG. 2, the heat collection temperature can be increased and the heat collection amount can be increased even when the circulation amount is the same as in the case of only CO ₂ .
[Embodiment 3]

Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 9 shows the heat medium of the present invention (dimethyl ether having a molar ratio of 7 to 35% with respect to CO ₂₎ as a secondary refrigerant of a Stirling refrigerator that uses the cold generated in the cooling section of the Stirling cycle as a cold heat source of the refrigerator. It is an embodiment in the case of using the (added). In FIG. 9, a refrigerant circulation line 22 through which a secondary refrigerant r ₂ made of CO ₂ and dimethyl ether flows is provided. One end of the refrigerant circulation line 22 is connected to the cooling unit 21 a of the Stirling refrigerator 21, and the other end is disposed in the cooling unit 24 of the refrigerator 23.

Cooling fins 25 are attached to the refrigerant circulation line 22 disposed in the cooling unit 24. Further, a circulating flow b is formed in the refrigerator 23 by the fan 26 so that the atmosphere in the refrigerator 23 hits the fins 25. The cooling unit 21 a of the Stirling refrigerator 21 is provided with a cylindrical expansion space (not shown). The secondary refrigerant r ₂ cooled by the primary refrigerant expanded and cooled in the expansion space reaches the cooling unit 24 in the refrigerator 23 through the refrigerant circulation line 22. In the cooling unit 24, the inside of the refrigerator 23 is cooled by the cold heat of the refrigerant through the refrigerant cooling fin 25.

The secondary refrigerant r ₂ absorbs heat in the refrigerator 23 at the cooling unit 24 of the refrigerator 23 and evaporates, and the secondary refrigerant r ₂ forms an ascending force u at the outlet side pipe 22 a of the cooling unit 24. The secondary refrigerant r ₂ is cooled and liquefied by the cooling unit 21 a of the Stirling cycle, and the liquid secondary refrigerant r ₂ flows into the cooling unit 24 of the refrigerator 23 and evaporates, and the rising force u of the Stirling refrigerator 21 Return to the cooling unit 21a. Thus secondary refrigerant r ₂ performs natural circulation without power. According to this embodiment, by using a refrigerant that was added from 7 to 35% of dimethyl ether in a molar ratio with respect to CO ₂ as a secondary refrigerant r _2, to obtain the same effect as the first embodiment Can do.

In addition, the heating apparatus using the heat | fever produced with the heating part of the Stirling refrigerator is also possible. In this case, natural circulation is enabled by the rising force of the evaporated secondary refrigerant and the liquid head formed by the liquefied secondary refrigerant liquid.
Since the heat medium of the present invention has good fluidity and does not decrease in viscosity even at high pressure and low temperature, the flow load can be reduced, so that natural circulation can be easily formed. In addition, since the amount of dimethyl ether added is 7 to 35 mol%, there is no restriction in terms of safety because it is not in a combustible region. Therefore, convenience can be improved.
[Embodiment 4]

Next, a fourth embodiment of the present invention will be described with reference to FIG. In FIG. 10, the heat medium c according to the present invention ( ₇ to 35% of dimethyl ether added to CO ₂ in a molar ratio) flows through the heat medium circuit 31. In the evaporation section 32 constituted by the evaporator 33, external heat is introduced to evaporate the heat medium c, and a supercritical state is formed in the outlet-side circulation flow path 31 of the evaporation section 32. The evaporated heat medium c dissipates heat in the liquefier 34 and liquefies. The heat radiated from the heat medium c is used as a heat source for the refrigerator 35, for example, an absorption refrigerator. A flow path switching / flow rate adjusting valve 36 is interposed on the upstream side of the evaporator 33.

In this embodiment, the evaporating section 32 is installed at a lower position than the liquefier 34, the outlet-side circulation channel 31a of the liquefier 34 is arranged in the vertical direction, and the liquid head H can be formed on the outlet side of the liquefier 34 It is configured. A natural circulation of the heat medium c is formed by the liquid head H and the ascending force of the heat medium c evaporated by the evaporation unit 32. In the present embodiment, the operational effects of using the heat medium c of the present invention and forming a natural circulation of the heat medium c are the same as those in the first embodiment.
[Embodiment 5]

  Next, a fifth embodiment of the present invention will be described with reference to FIG. In FIG. 11, an evaporator 42 and a liquefier 44 composed of a plurality of evaporators 43 are interposed in the circulation channel 41 of the heat medium c. This embodiment is an embodiment in which the installation location of the evaporation unit 42 is high due to restrictions on the installation location, and it is not easy to form a natural circulation only with the liquid head H formed on the outlet side of the liquefier 44. . Therefore, an auxiliary pump 45 for assisting natural circulation of the heat medium c is provided in the circulation channel 41. A flow path switching / flow rate adjusting valve 47 is interposed upstream of the evaporator 43.

  In this embodiment, circulation of the heat medium c is formed with the help of the liquid head H and the auxiliary pump 45. The heat medium c is introduced into the evaporation unit 42, the heat medium c absorbs heat from the outside in the evaporation unit 42, and the heat medium c is transferred to the liquefier 44 in a liquid or gas state on the outlet side of the evaporation unit 42. . In the liquefier 44, the latent heat of the heat medium c is absorbed as a heat source of the refrigerator 46, for example, an absorption refrigerator. The heat medium c in which the latent heat has been absorbed by the liquefier 44 is liquefied, stored in the liquefier 44, and then transferred to the evaporation unit 42 by the pump 45.

In the present embodiment, a heat medium in which 7 to 35% of dimethyl ether is added to CO ₂ in a molar ratio is used as the heat medium c. Therefore, the same operational effects as those in the first embodiment can be obtained except that the power of the auxiliary pump 45 is required.
[Embodiment 6]

Next, a sixth embodiment of the present invention will be described with reference to FIG. This embodiment is an embodiment when the refrigerant of the present invention is applied to the cooling device 50 as a secondary refrigerant. In FIG. 12, in the refrigerator 51, a primary refrigeration cycle is configured in a primary circulation passage 52 through which a primary refrigerant r ₁ flows, and the circulation passage 52 is connected to a heat exchanger 53. On the other hand, the two flows a secondary coolant r ₂ primary circulation flow path 54 (the secondary refrigeration cycle) is connected between the heat exchanger 53 and the heat load 55 (the space to be air-conditioned r). The secondary refrigerant r2 is forcibly circulated by the pump 56.

Secondary refrigerant r ₂ is a refrigerant having a structure of the present invention. By primary refrigerant r ₁ in the heat exchanger 53 is evaporated takes heat from the secondary coolant r _2, the secondary refrigerant r ₂ is cooled. The cooled secondary refrigerant r ₂ cools the heat load 55 (air-conditioning target space r). The secondary refrigerant r ₂ is circulated through the circulation flow path 54 while being in a liquid state, and the cooling unit 50 is a cooling unit using the sensible heat of the secondary refrigerant r ₂ .

According to the present embodiment, since the heat transfer medium of the present invention ( ₇ to 50% of dimethyl ether added to CO ₂ in a molar ratio) is used as the secondary refrigerant r ₂ , Examples 1 and 2 in FIG. As shown in FIG. 6, since the critical temperature rises, the condensation temperature rises and the condensation easily occurs. Therefore, since it can condense with normal temperature water or air, the convenience improves. Conversely, since the saturation pressure is reduced, the operating pressure is reduced, and therefore, the secondary circulation flow path 54 and the devices interposed in the secondary circulation flow path 54 can be set to low pressure specifications, thereby reducing the apparatus cost. can do.
Further, the melting point of dimethyl ether is −146 ° C. with respect to the melting point of CO ₂ -56.6 ° C., and the addition of dimethyl ether further lowers the melting point. A heat transfer device using a refrigerant is also possible.

Further, as shown in Examples 2, 4 and 5 in FIG. 2, the heat retention amount increases, and thereby the heat transfer amount also increases. For this reason, in the forced circulation, the heat transfer efficiency is improved. Furthermore, since it is nonflammable or weakly flammable, it is safe. If the addition amount of dimethyl ether is 1 to 12 mol%, it becomes nonflammable, so there is no risk of ignition even in a cooling device disposed indoors or in a closed space.
[Embodiment 7]

Next, a seventh embodiment of the present invention will be described with reference to FIG. In FIG. 13, in the refrigerator 61, a primary refrigeration cycle is configured in a primary circulation channel 62 through which a primary refrigerant r ₁ flows, and the circulation channel 62 is connected to a heat exchanger 63. On the other hand, the secondary refrigerant r ₂ flows through the secondary circulation flow path 64 (secondary refrigeration cycle), and the secondary refrigerant r ₂ is the refrigerant according to the present invention (1 to 12% of dimethyl ether is added to CO ₂ at a molar ratio). Stuff).

In addition to the heat exchanger 63, the secondary circulation flow path 64 is provided with a compressor 65, an evaporator 66, and an expansion valve 67 to constitute a secondary refrigeration cycle. The primary refrigerant r ₁ is deprived of the latent heat of evaporation by the heat exchanger 63 and the secondary refrigerant r ₂ is cooled to −20 ° C. On the other hand, in the evaporator 66 of the secondary circulation flow path 64, can be secondary coolant _{r 2} is deprives vaporization latent heat from the heat load 68 to cool the heat load 68 below -40 to-50 ° C. or -56 ° C. . Thus, this embodiment constitutes a cascade refrigerator 60 having a dual refrigeration cycle.

According to this embodiment, since the secondary refrigerant r ₂ is added with 1 to 12% of dimethyl ether in a molar ratio with respect to CO ₂ , the fluidity is excellent, and by adding dimethyl ether to CO ₂ , Condensation temperature rises and the condensation temperature rises and the saturation pressure decreases. Since the saturation pressure is reduced, the design pressure strength can be reduced, so that the initial cost can be reduced.
The secondary refrigerant r ₂ is because it has a non-flammable, but may be used for indoor or enclosed space, the convenience is improved.

According to the present invention, in a heat transfer device such as a refrigeration facility or a heat pump facility, a heat transfer medium in which dimethyl ether is added to CO ₂ is used, thereby improving thermal efficiency, improving convenience, and a safe heat transfer device. Can be realized.

It is a graph which shows the Example (critical temperature rise test) of this invention. It is a graph which shows the Example (physical property and heat retention comparison) of this invention. It is a graph which shows the Example (natural circulation; heat collection comparison) of this invention. It is a graph which shows the Example (evaporator heat transfer test) of this invention. It is a graph which shows the Example (combustion safety evaluation) of this invention. It is a graph which shows the Example (viscous resistance of natural circulation) of this invention. It is a systematic diagram of a 1st embodiment of the present invention. It is a systematic diagram of 2nd Embodiment of this invention. It is a systematic diagram of 3rd Embodiment of this invention. It is a systematic diagram of 4th Embodiment of this invention. It is a systematic diagram of 5th Embodiment of this invention. It is a systematic diagram of 6th Embodiment of this invention. It is a systematic diagram of 7th Embodiment of this invention.

Explanation of symbols

1 Heating device (heat transfer equipment)
2, 11, 31, 41 Heat medium circulation path (natural circulation heat pump cycle)
3 Evaporator 4 Heat Recovery Unit 5, 6 Heat Transfer Tube 10 Solar Heat Collector (Heat Transfer Facility)
12 heat collector 13, 53, 63 heat exchanger 21 Stirling refrigerator 22 secondary refrigerant circulation line 23 refrigerator (heat load)
32, 42 Evaporating section 34, 44 Liquefaction unit 45 Auxiliary pump 50 Cooling device (heat transfer equipment)
52,62 Secondary circulation channel (primary heat pump cycle)
53,63 Heat exchanger 55,68 Thermal load 60 Cascade refrigerator (heat transfer equipment)
c Heat medium (heat transfer medium)
H liquid head r ₁ primary refrigerant r ₂ secondary refrigerant (secondary heat transfer medium)
u Climbing force

Claims (7)

In a heat transfer device using a heat transfer medium mainly composed of CO ₂ as a heat transfer medium in a heat transfer facility for cooling or heating purposes,
A heat transfer medium obtained by adding 1 to 50% of dimethyl ether in a molar ratio to CO ₂ is interposed between the heat exchanger of the primary heat pump cycle and the heat load, and heat between the primary heat pump cycle and the heat load. A heat transfer device that is used as a secondary heat transfer medium that performs transmission. In a heat transfer device using a heat transfer medium mainly composed of CO ₂ as a heat transfer medium in a heat transfer facility for cooling or heating purposes,
The heat transfer facility includes a natural circulation heat pump cycle that circulates the heat transfer medium by a temperature difference and a liquid head difference without interposing a physical forced circulation device with compression or lifting action of the heat transfer medium,
A heat transfer device, wherein a heat transfer medium obtained by adding 1 to 35% of dimethyl ether in a molar ratio to CO ₂ is used in the heat pump cycle. It is installed indoors or closed space, heat transfer device according to claim 2, wherein the heat transfer medium is characterized by being added from 1 to 12% of dimethyl ether in the molar ratio CO _2.   The heat transfer device according to claim 2, wherein an auxiliary pump for assisting circulation of the heat transfer medium is interposed in the heat transfer medium circulation path of the heat pump cycle. In a heat transfer medium mainly composed of CO ₂ used as a heat transfer medium in a heat transfer facility for cooling or heating purposes,
A heat transfer medium obtained by adding 1 to 50% of dimethyl ether in a molar ratio to CO ₂ is interposed between the heat exchanger of the primary heat pump cycle and the heat load, and between the primary heat pump cycle and the heat load. A heat transfer medium which is used as a secondary heat transfer medium for a heat pump cycle which performs heat transfer. In a heat transfer medium mainly composed of CO ₂ used as a heat transfer medium in a heat transfer facility for cooling or heating purposes,
A heat transfer medium comprising a heat transfer medium obtained by adding 1 to 35% of dimethyl ether in a molar ratio to CO ₂ as a heat transfer medium of a natural circulation heat pump cycle. The heat transfer medium according to claim 6, wherein the heat transfer medium is obtained by adding 1 to 12% of dimethyl ether in a molar ratio to CO ₂ , and the heat transfer equipment is installed indoors or in a closed space.

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