JP5317000B2 - Air conditioning system for ships using cold LNG and seawater - Google Patents

Description

  The present invention relates to an air conditioning system for a ship using LNG cold and seawater as a cooling source.

Use drawings.

In the ship LNG fuel system, LNG is vaporized and heated with steam, seawater, or air in order to obtain the normal temperature LNG gas required for fuel supply to the main engine. It is thrown away.
(For example, Reference 1)

In conventional air conditioning systems using LNG cold heat, there is no direct cooling / condensation method of refrigerant using LNG cold heat, which complicates the device configuration and operation method, and also increases costs economically. Become.
(For example, Patent Document 2 and Patent Document 3)

The use of LNG cooling is not switched to condensing refrigerant or supercooling refrigerant liquid according to the excess or deficiency of the amount of cooling obtained from LNG with respect to the required amount of cooling of the air conditioning system. In addition, when the LNG cold heat is insufficient for the heat of condensation of the refrigerant, the LNG cold heat is not used and is discarded to the outside, and no contribution to the air conditioning system is made.
(For example, Patent Document 2)

Since the refrigerant may freeze due to the extremely low temperature of LNG when using cold LNG, it is necessary to limit the heat transfer tube structure to prevent freezing or the range of cold energy used by LNG. Absent.
(For example, Patent Document 4 and Patent Document 5)

Regardless of the LNG flow rate and the air conditioning load fluctuation, the gas temperature before entering the main engine after the temperature rise needs to be constant, but when the cold heat of the LNG is excessive with respect to the air conditioning load, the cooling of the refrigerant And cooling the brine by the same cold recovery unit, and there is no mechanism to perform appropriate refrigerant cooling, cold storage and LNG gas temperature increase at the same time.
(For example, Patent Document 2 and Patent Document 3)

In order to smoothly operate the air conditioning system using brine, it is desirable to supply a cooling source having a constant temperature. For this purpose, it is necessary to store the brine after cooling it at a constant temperature. Conventionally, however, cold storage and storage at a constant temperature have not been performed.
(For example, Patent Document 2 and Patent Document 3)

In the case of air cooling with brine, temperature adjustment of the regenerator material supplied to the evaporator is not necessary in order to prevent the air temperature from being overcooled due to the excessively low temperature of the regenerator material.
(For example, Patent Document 2 and Patent Document 3)

When the refrigerant condensed by the cold heat of LNG is sent to the air cooler, the condensing pressure is reduced as much as possible by utilizing the fact that the condensing temperature is lower than that by the seawater cooling, and the compressor is downsized or a small fan accordingly. The energy-saving refrigerant circulation system consisting of replacement by and transfer of refrigerant liquid by a pump is not considered.
(For example, Patent Document 2 and Patent Document 3)

When the refrigerant condensed by the cold heat of LNG is sent to the air cooler, as an alternative to the above [0009], in the refrigerant circulation system of this application, the condensation temperature is set to be lower than the evaporation temperature, and the refrigerant is circulated using a compressor. However, this method does not take into consideration the further energy-saving refrigerant circulation method.
(For example, Patent Document 2 and Patent Document 3)

When the refrigerant liquid condensed by the cold heat of LNG by means of the above [00010] is circulated by a pump, the degree of supercooling of the refrigerant is excessive, and it is inconvenient to send it directly to the vapor. Therefore, it is necessary to adjust the degree of supercooling by increasing the temperature of the refrigerant liquid before entering the evaporator, but this has not been considered in the past.
(For example, Patent Document 2 and Patent Document 3)

When there is no LNG or brine as a cold heat source, it is necessary to switch to a cooling method of the refrigerant with seawater, but there is no combination of both cooling sources in one apparatus.
(For example, see Document 1, Patent Document 2, Patent Document 3, Patent Document 4, and Patent Document 5)
Japanese Patent Laid-Open No. 2004-211949 JP-A-6-313687 JP-A-8-157840 JP 2008-202652 A

Reference 1

  Latest Trends in LNG Transportation Technology, Kazuaki Yuasa, Oil / Natural Gas Review, VOL. 42 no. 4, July 2008

  LNG transport ships that use LNG as the main fuel of a ship have a small proportion of the ship as a whole, so the significance of using the cold energy of LNG has been weak. In order to protect the global environment and prevent air pollution in the sea area by an international organization related to nautical affairs, LNG with a low environmental load is used as fuel for all ships of any ship type in a wide range of exhaust gas restricted areas. It is obliged to use as. In response to changes in the marine transportation environment such as the rapid increase in the number of LNG fueled ships, the significance of environmentally-friendly ships that combine the use of LNG cold energy and the energy saving of air-conditioning systems increases.

  The flow rate of LNG determined by the load of the main engine of the ship or the navigational sea area subject to fuel regulation by exhaust gas components and the required amount of cold heat of the air conditioning system are systems that arbitrarily change without being related to each other. Therefore, it is necessary to construct a system in which changes in the supply and demand of cold are not affected by the other.

  Even when the flow rate of LNG is excessive with respect to the cooling load of the air conditioning system, the excess cooling heat of LNG after being recovered by the air conditioning system can be recovered in another form without being thrown away to the outside. It is desirable to be used for

  Even when the cooling load required for the air conditioning system is larger than the cooling heat obtained from LNG, there is a need for a system that can be effectively used for the air conditioning system without throwing away the LNG cooling heat.

  When the cold heat of LNG is stored in brine and air cooling is performed with the brine, it is important to keep the temperature of the low-temperature brine sent to the air cooler constant for smooth control of the air conditioning system. For this purpose, the temperature of the brine to be cooled is controlled to be constant, and a storage tank and a receiving tank are required to be independent from each other for brine storage.

  In the conventional seawater cooling and refrigerant circulation system using a compressor, the condensation pressure is high because the condensation temperature is high, and the power of the compressor must be increased as the compression ratio increases. There was no art. At the same time, the refrigerant circulation must rely on a gas compressor, and the gas compression requires a large driving power.

  When a refrigerant or brine having a freezing point higher than the temperature of LNG is used as a cold recovery medium, a special structure or temperature management is important for avoiding the solidification of the refrigerant or brine in the heat recovery heat exchanger. It is.

  Similarly, as another means for avoiding the solidification of the refrigerant, a heat exchanger configuration capable of selectively using the recovered cold heat depending on the latent heat of the LNG and the sensible heat is also important, focusing on the amount of the cold heat of the LNG.

  When the flow of LNG is stopped due to the navigational sea area or the state of the main engine, or when the stored low-temperature brine is exhausted, the conventional seawater system can be used as a cooling source for the air conditioning system to maintain the continuous operation of the air conditioning system. It is important that they are incorporated in advance and can be switched by simple valve operation.

  In order to solve the above-described problems, the invention according to claim 1 collects all of the LNG from the latent heat to the sensible heat of room temperature gas, regardless of fluctuations in the flow rate of LNG to the main engine or fluctuations in the load of the air conditioning system. The refrigerant is circulated in the air-conditioning system by cooling the refrigerant and the brine in the air-conditioning system and with a little power compared to the conventional seawater cooling. When there is no LNG, the air is directly cooled by the cold-stored brine, and when there is no cold storage, the refrigerant is condensed by seawater. As described above, the heat characteristics of LNG, brine, and seawater are appropriately combined to use the cold energy of LNG as a cooling source of the air conditioning system without waste.

  In the invention according to claim 2, in the case where the refrigerated cold energy of LNG is insufficient to condense all the refrigerant, the refrigerant is condensed by seawater in advance and then recovered from the LNG by the cold heat lower than the refrigerant liquid. So-called supercooling is performed. In this case, a tube system that can switch whether the LNG cooling utilization range is the total cooling of latent heat and sensible heat or only sensible heat according to the degree of necessity of supercooling. As a result, the cooling capacity of the air conditioning system can be increased without wasteful use of the recovered cold heat from LNG that is insufficient for the heat of condensation of the refrigerant.

  In the invention according to claim 3, a brine line is provided at the same time as the refrigerant line in the LNG cold heat recovery device, and the cold heat of LNG that is excessive for cooling the refrigerant is recovered by circulation of the brine and stored in the tank. The brine is stored in the storage tank by controlling the flow rate so that the brine is cooled to a preset constant temperature. When the air conditioning system is operated by the cold storage agent, brine having a constant temperature is supplied from this tank to the air cooler, returned to the other tank, and stored. The stable operation of the air conditioning system becomes possible by supplying brine at a constant temperature.

  In the invention according to claim 4, when air cooling is directly performed with brine, in order to prevent air overcooling due to an excessively low temperature of the brine or a problem of water coagulation, a part of the brine that has been heated after the air cooling is removed at the entrance. Return to the brine supply side, mix, and supply the brine adjusted to a constant temperature. This allows the air temperature to be optimized and the air cooler to operate smoothly.

  In the invention according to claim 5, the flow in the pipe when the refrigerant gas after leaving the evaporator is increased to a pressure slightly higher than the evaporation pressure and further sent to the main engine room located on the lower deck, And a small fan or a small compressor with the smallest possible pressure consisting of the flow resistance in the cold heat recovery unit and a slight positive pressure, pumping out the condensed refrigerant liquid by collecting cold heat with LNG Lift up to the air conditioner room located on the upper deck and send it to the evaporator via the expansion valve. Alternatively, (2) the refrigerant gas after leaving the evaporator is sent to the main engine room on the lower deck, the pressure is adjusted by the pressure reducing valve, the refrigerant is sent to the cold heat recovery unit, and the refrigerant liquid condensed at a pressure lower than the evaporation pressure is supplied. The pump is lifted to the air conditioner room on the upper deck, and the excess supercooling is heated by the heater and then sent to the evaporator via the expansion valve. Equipped with either method (1) or (2), refrigerant condensation is performed by collecting cold heat at an appropriate temperature in each of (1) and (2), and at the same time, the refrigerant circulation power is greatly increased. It can be made smaller.

  In the invention according to claim 6, the heat transfer tube provided in the LNG cooler is made of a double structure such as stainless steel, and the interior space is filled with an inert gas such as nitrogen gas or helium gas, or an incombustible material such as glass fiber. The heat transfer between the inside and outside of the pipe is limited. As a result, the temperature of the outer surface of the heat transfer tube is maintained at a certain level or more, so that the solidification of the refrigerant or brine can be prevented.

  In the invention according to claim 7, the heat transfer tube provided in the LNG cold heat recovery device is made of stainless steel or the like, and the outer surface thereof is covered with a high thermal conductivity skin material such as copper. When a low-temperature spot is partially generated by this, the low temperature is rapidly dispersed in the periphery by utilizing the physical properties of high thermal conductivity such as copper material, and the temperature of the refrigerant or brine It becomes possible to prevent coagulation.

  In the invention according to claim 1, by using the cryogenic cold energy of LNG for the condensation and supercooling of the refrigerant of the air conditioning system, the excess cold energy is stored in brine at the same time, so that it is usually discarded in the atmosphere, seawater or water vapor. By effectively recovering the thermal energy consumed for vaporizing and raising the temperature of LNG and using it as a cooling heat source for the air conditioning system, the operating power of the air conditioning system can be greatly reduced. is there. At the same time, the heat energy for the conventional heat medium consumed for LNG gasification becomes unnecessary, and double energy saving becomes possible. When there is no LNG, direct air cooling with cold storage brine is performed, and when there is no cold storage brine, the refrigerant is condensed with normal seawater and switched to a large compressor drive system. These operation conversions can be easily switched only by valve operation, and continuous operation of the air conditioning system is possible.

  In the invention according to claim 2, when the amount of heat recovered from the LNG is insufficient to condense the refrigerant, the refrigerant is first condensed in seawater, and then the LNG cold is used to supercool the refrigerant liquid. By using it, it is possible to effectively utilize the LNG cold without leaving it and to increase the cooling capacity of the air conditioning system. Further, according to the necessity of supercooling, flexible use of cold energy can be achieved by adjusting whether the cold heat of LNG to be used is the total amount of latent heat and sensible heat or only sensible heat.

  In the invention according to claim 3, when the amount of cold heat of LNG exceeds the amount of cold heat necessary for the air conditioning system, the air conditioning system recovers only the amount of cold heat necessary, and the remaining amount of LNG cold heat is a separately provided cold storage brine. It is recovered at a constant temperature through the system and stored in a brine tank dedicated to LNG cold recovery. When there is no LNG, the low-temperature brine from the tank is directly circulated as a cooling source for air cooling, and the recovered brine is stored in a dedicated brine recovery tank. As a result, a constant temperature cooling source is obtained, and stable operation of the air conditioning system is achieved.

  In the invention according to claim 4, when the stored brine is sent to the air cooler, if the temperature of the brine is too low, the air temperature is too low or moisture coagulation occurs. Therefore, the brine that has been heated through the air cooler is once returned to the inlet side, and the brine at a temperature suitable for air cooling can be supplied by adjusting the mixing of the super low temperature brine and the heated brine.

  In the invention according to (1) out of claim 5, taking advantage of the environment in which the condensation temperature and the condensation pressure of the refrigerant can be lowered when using LNG cold heat, first the condensation pressure is set to a level slightly higher than the evaporation pressure, The refrigerant is condensed and circulated at a pressure as small as possible by adding a slight positive pressure to the piping resistance of the refrigerant circulation and the refrigerant flow resistance in the condenser. As a result, the refrigerant vapor can be driven by a small compressor or fan, resulting in a significant energy saving effect.

  In the invention relating to item (2) in claim 5, as an alternative to item (1), the refrigerant is condensed at a temperature lower than the evaporation temperature, and the condensed refrigerant liquid is circulated by a pump. In this case, since the condensate is considerably supercooled, the temperature is once raised by a heater and adjusted to an appropriate liquid temperature. As a result, the refrigerant can be circulated only by the liquid pump, and the driving power can be greatly reduced.

  In the invention according to claim 6, by keeping the surface temperature of the heat transfer tube of the heat exchanger used for LNG cold recovery at or above the freezing point of the refrigerant or brine, it is avoided that the refrigerant or brine is solidified on the surface of the tube. Thus, a smooth flow of refrigerant or brine and an appropriate heat transfer function are maintained.

  In the invention according to claim 7, even if the surface temperature of the heat exchanger tube of the heat exchanger used for LNG cold recovery is locally reduced below the freezing point of the refrigerant or brine, the high thermal conductivity provided on the tube surface is high. Depending on the material, a conductive heat flow is generated from the relatively hot part of the surroundings, which acts in the direction of temperature dispersion and uniformity. As a result, the partial low temperature is eliminated, the refrigerant or brine is prevented from solidifying on the surface of the pipe, and a smooth flow of the refrigerant or brine and an appropriate heat transfer function are maintained.

  An object of the present invention is to realize a highly efficient and energy-saving air conditioning system that contributes to the improvement of the global environment by utilizing the cold heat of LNG as an effective cooling heat source of the air conditioning system. At the same time, natural refrigerant carbon dioxide (hereinafter abbreviated as CO2) cannot be condensed in seawater because it has a lower critical temperature than ordinary alternative chlorofluorocarbon refrigerants, and at a high pressure of about 10 MPa. Although compression was required and cooling capacity had to be reduced as a result, the present invention facilitates the use of CO2 as a refrigerant, and promotes the use of a CO2 refrigerant with a low global warming potential and no ozone layer destruction. And contribute to the global environment.

The energy saving, the cooling effect increase, and the contribution to the global environment according to the present invention will be described. Here, COP is a value obtained by dividing the cooling capacity by the required power of the refrigerant circulation device, and represents the cooling capacity per required energy. Although CO2 and alternative Freon R404A are targeted as natural refrigerants, similar results are obtained with other refrigerants.
When both the latent heat and sensible heat of LNG are recovered for both refrigerants, the cooling capacity is approximately 1.7 times, and at the same time, the COP is increased by an order of magnitude due to the reduction of the circulation power of the refrigerant. In the case of recovering only sensible heat of LNG, the cooling capacity is about 1.7 times, and the COP is about twice. By implementing the present invention in this way, significant energy savings are possible. For CO2, which has a low critical temperature, the present invention can reduce the condensing temperature and the condensing pressure is about 4 MPa, less than half, making it possible to make the equipment lighter, making it easier to use as a refrigerant while reducing costs. It becomes.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS. As a refrigerant, a non-fluorocarbon natural refrigerant CO2 and a general alternative fluorocarbon R404A will be described as target examples. The same applies to the case of using other refrigerants.

  FIG. 1 shows a fuel system in a conventional LNG fuel ship and a refrigerant system of an air conditioning system, both of which are independent systems regardless of each other. That is, the cold energy recovery of LNG is not made.

  FIG. 2 shows that the LNG's latent heat and sensible heat, or the sensible heat, is directly recovered by a refrigerant and the air conditioning system is operated by the refrigerant. At the same time, excess cold heat is recovered and stored by brine. It is a systematic diagram which operates an air-conditioning system by this cold storage heat. The seawater cooling system is also shown.

  FIG. 3 shows the structure of the heat transfer tubes of the LNG and refrigerant, and the LNG and brine heat exchangers designed to avoid the solidification of the refrigerant during LNG cold recovery according to this embodiment.

  4 to 9 are ph diagrams showing changes in pressure and enthalpy along the refrigerant flow in the air conditioning system according to the present embodiment, with the vertical axis representing pressure and the horizontal axis representing enthalpy. This represents a state of improvement in cooling capacity and reduced power for refrigerant circulation.

The operation of the conventional air conditioning system will be described with reference to FIG.
A shows the refrigerant | coolant system | strain by the seawater cooling of the air-conditioner room installed in an upper deck.
B represents the LNG fuel system in the main engine room installed on the lower deck.
The refrigerant liquid is squeezed and expanded by the expansion valve 6 and enters the evaporator 7, where the air is cooled to become vapor, compressed to the condensation pressure by the compressor 8, and enters the seawater condenser 9. The condensed liquid returns to the expansion valve 6 through the refrigerant pipe 10. During this time, the cold energy necessary for condensation of the refrigerant is obtained from seawater. Since the temperature of seawater is as high as about 32 ° C., the condensation temperature is as high as about 40 ° C., and therefore the condensation pressure is also high. For this reason, the compressor 8 is required to have a large compression ratio, and the required power of the compressor increases. On the other hand, the LNG system flows from the supply pipe 1 to the evaporator 2, where it is heated and vaporized by water vapor and enters the LNG heater 4 from the LNG vapor pipe 3, where it is heated to room temperature by water vapor and passes through the gas pipe 5. To be supplied. That is, all the heat required for LNG vaporization and gas temperature rise is provided by high-temperature steam.

The functions of the systems C, D, E, F, G, and H will be described with reference to FIG.
System C shows the case where the refrigerant is supercooled with LNG cold and the case of seawater cooling, and this system is generally installed in the air conditioner room on the upper deck.
The system D condenses the refrigerant with LNG cold heat, shows refrigerant circulation by a small compressor or a fan and a pump, and is generally installed in the air conditioner room on the upper deck.
The system E condenses the refrigerant with LNG cold and shows the case of refrigerant circulation using only the pump, and is generally installed in the air conditioner room on the upper deck.
System F indicates a LNG cold recovery system and is generally installed in the main engine room on the lower deck.
The system G shows the cold energy of LNG stored in brine, and is generally installed in the main engine room on the lower deck.
System H indicates air cooling by brine stored by LNG cold, and is generally installed in the air conditioner room on the upper deck.
The evaporators 26C, 26D, 26E and 26H described in the figure all represent the same air cooler, and the evaporation temperature and the evaporation pressure, which are operating conditions, are determined from the specifications of the air conditioning system and are all the same. Only 26H is cooled only by the temperature change of the brine solution. In actual use, it is connected to one of the pipe systems according to the method.

  First, the LNG cold recovery system F will be described with reference to FIG. LNG enters the LNG evaporator 12 from the supply pipe 11 and is vaporized by the cooling heat of the refrigerant and brine. Thereafter, it enters the heater 14 through the pipe 13, where the temperature is similarly raised by the cooling heat of the refrigerant and brine, and is led from the LNG gas pipe 15 to the main engine. During this time, the cold heat of LNG is recovered in the form of condensation or supercooling by cooling the refrigerant and brine. When the air conditioning system is not used, LNG is evaporated and heated by steam 48 and steam 47.

  The pump 20 that circulates the refrigerant after recovering the cold heat of LNG will be described with reference to FIG. Of the pump points necessary for circulation of the three types of refrigerants C, D, and E, the refrigerant flow rate is almost equal in all cases, and the same pump is used. A slightly different discharge pressure is adjusted by the discharge pressure control valve 21. Alternatively, separate pumps can be provided.

  The system C in the case of supercooling the refrigerant will be described with reference to FIG. The refrigerant liquid once condensed by the seawater cooler 28 passes through the valve 23B and is cooled only by the LNG evaporator 12 and the heater 14 or the heater 14 according to the degree of supercooling to become supercooled liquid. When only sensible heat is recovered, the valve 18 is closed and the bypass valve 19 is opened. The supercooled refrigerant reaches the expansion valve 25 through the refrigerant circulation pump 20, the discharge pressure control valve 21, the valve 23 </ b> A and the refrigerant pipe 24. The evaporator 26C evaporates at a predetermined temperature and pressure, and then returns to the seawater condenser via the large compressor 27. During this time, the valve 30, pipe 31 or pipe 34 of the refrigerant system is closed.

  The system D in the case of circulating the refrigerant | coolant which collect | recovered the cold heat | fever of LNG and condensed with FIG. 2 with a small power compressor or a small power fan and pump is demonstrated. The LNG evaporator 12 and the heater 14 recover the latent heat and sensible heat of the LNG, and the refrigerant condensed at a temperature and pressure slightly higher than the evaporation temperature and pressure passes through the refrigerant circulation pump 20 and the discharge pressure control valve 21 as a refrigerant pipe. 22 and the refrigerant pipe 31 to the expansion valve 32. Next, the expansion valve 32 decompresses and expands to a predetermined evaporation pressure, evaporates in the evaporator 26D, and performs air cooling. Thereafter, the pressure is increased to a slight positive pressure by a small compressor or a fan, passes through the refrigerant pipe 38, and returns to the LNG cold recovery circuit. During this time, the pressure increase in the compressor or fan is very small because it is only necessary to add the pressure loss in the cold heat recovery circuit to the condensing pressure slightly higher than the evaporation pressure, and therefore the required power is also small. The role of the refrigerant circulation pump 20 is to have the total pressure of the vertical drop from the main engine room on the lower deck to the air conditioner room on the upper deck and the resistance of the pipe system between them and the operating pressure of the expansion valve. small. The discharge pressure is controlled by the discharge pressure control valve 21.

  Similarly, FIG. 2 illustrates another method for circulating the condensed refrigerant, that is, a system E of a system that operates only by a pump. In the same manner as described above, the latent heat and sensible heat of LNG are recovered, and the refrigerant condensed at a temperature and pressure lower than the evaporation temperature and pressure passes through the refrigerant circulation pump 20 and the discharge pressure control valve 21 to form the refrigerant pipe 22 and the refrigerant pipe 34. The refrigerant liquid is further heated to an appropriate supercooling temperature by the heater 35 and reaches the expansion valve 36. Next, the expansion valve 36 decompresses and expands to a predetermined evaporation pressure, evaporates in the evaporator 26E, and performs air cooling. Next, the refrigerant gas exiting the evaporator is depressurized by the pressure reducing valve 37 until the condensing pressure is met, and returns to the LNG cold heat recovery circuit. During this time, the refrigerant circulation pump 20 plays a role of the vertical drop from the main engine room on the lower deck to the air conditioner room on the upper deck, the resistance of the pipe system between them, the operating pressure of the expansion valve, the resistance of the evaporator and the LNG cold heat recovery unit The required power is small in order to have the total pressure. The discharge pressure is controlled by the discharge pressure control valve 21.

  With reference to FIG. 2, the LNG cold storage system G using brine will be described. The brine that leaves the brine tanks B and 40B and is circulated by the brine pumps B and 41B recovers cold heat by the heater 14 and the LNG evaporator 12. During this time, the brine flow rate is controlled by the brine flow rate control valve 46 so as to reach a constant temperature at the outlet point 39 and stored in the brine tanks A and 40A.

  The system H in the case of air cooling with brine stored cold will be described with reference to FIG. The brine that leaves the brine tanks A and 40A and is circulated by the brine pumps A and 41A is supplied to the evaporator 26H via the brine pipe 42, and air cooling is performed only by the temperature change of the brine solution. When the brine temperature is excessively low, a part of the heated brine is returned to the upstream side of the evaporator 26H by the pipe 43 and the brine circulation valve 44 and adjusted to an appropriate temperature. After that, they are returned to the brine tanks B and 40B and stored.

  A case where both LNG and cold-storage brine are not used, and only seawater is operated will be described with reference to FIG. The refrigerant is condensed by seawater in the seawater condenser 28, passes through the refrigerant pipe 29, the refrigerant valve 30, the refrigerant pipe 24, and the expansion valve 25, and is evaporated at a predetermined temperature and pressure in the evaporator 26 </ b> C. After that, it returns to the seawater condenser 28. During this time, the refrigerant valve 23A and the refrigerant valve 23B are closed.

  FIG. 3 shows a heat transfer tube structure of a heat exchanger for LNG cold recovery provided to avoid solidification of refrigerant or brine. Refrigerant or brine 49 and LNG 50 flow outside and inside the heat transfer tube. Both fluids include a high thermal conductivity coating material 51 (for example, copper tube), a low thermal conductivity outer tube 52 (for example, stainless steel), a low thermal conductivity support material 54 (for example, stainless steel or a non-metallic material), and a low thermal conductivity inner tube 53 (for example, Stainless steel). The space between both the inner and outer tubes is filled with an inert gas 55 (for example, nitrogen or helium) or an incombustible heat insulating material 55 (for example, glass fiber). With this structure, first, the low heat transfer structure appropriately prevents a temperature drop on the tube surface on the opposite side due to the cryogenic LNG. Further, the local low-temperature portion is subjected to temperature dispersion by heat conduction in the planar direction of the outermost high-heat-conductive coating material 51, and the low-temperature portion is eliminated. Selection of these materials and dimensions can be made by heat transfer calculation.

The relationship between the air conditioning system and the main engine fuel system in the conventional LNG ship is shown, and both are independent of each other. The system diagram in the case where the cold heat of LNG by this embodiment is directly collect | recovered with a refrigerant | coolant or a brine, and an air conditioning system is operated with this refrigerant | coolant or a brine is shown. The structure of the heat exchanger tube of the heat exchanger of the LNG cold heat recovery for avoiding solidification of the refrigerant | coolant and brine by this embodiment is shown. The P (pressure) -h (enthalpy) diagram in the case of natural refrigerant | coolant CO2 in the normal system only by seawater cooling is shown. A cooling capacity line indicated by a double-headed arrow represents a portion that exhibits a cooling effect, and exhibits a cooling effect in proportion to this length. Similarly, the amount of compression work is indicated by a double arrow, and compression power proportional to this length is required. This is common to all the following figures. Refrigerant circulation in the case of seawater cooling is performed by a large compressor. The case where LNG total cold heat | fever is collect | recovered with the CO2 refrigerant | coolant by this invention is shown. The cooling capacity is greatly increased by the decrease in the condensation temperature, and at the same time, the compression work is reduced and the COP is greatly improved. The case where the refrigerant circulation is performed by a small compressor or a fan is the upper stage side, and the case where the refrigerant circulation is performed by a pump is the lower stage side. The case where the refrigerant once condensed in seawater by the cold heat of LNG with the CO2 refrigerant according to the present invention is shown. As the degree of supercooling increases, the cooling capacity increases by the length indicated by the arrow, and at the same time COP is improved. Since the condensation of the refrigerant is seawater cooling, the refrigerant is circulated by a large compressor. The case of the alternative chlorofluorocarbon refrigerant R404A in the normal method using only seawater cooling is shown. Since it is seawater cooling, the refrigerant is circulated by a large compressor. The case where the LNG total cold heat | fever is collect | recovered with the R404A refrigerant | coolant by this invention is shown. The cooling capacity is greatly increased by the decrease in the condensation temperature, and at the same time, the COP is greatly improved. When the refrigerant circulation is performed by a small compressor or a fan, the upper stage side is used, and when the refrigerant circulation is performed by a pump, the lower stage side is used. The case where the refrigerant | coolant once condensed with seawater with the cold of LNG with the R404A refrigerant | coolant by this invention is shown. As the degree of supercooling increases, the cooling capacity increases by the length indicated by the arrow, and at the same time COP is improved. Since the condensation of the refrigerant is seawater cooling, the refrigerant is circulated by a large compressor.

1: LNG supply pipe 2: LNG evaporator 3: LNG steam pipe 4: LNG heater 5: LNG gas pipe 6: expansion valve 7: evaporator 8: compressor 9: seawater condenser 10: refrigerant pipe A: seawater cooling refrigerant System, air conditioning room, upper deck installation B: LNG fuel system, main engine room, lower deck installation 11: LNG pipe 12: evaporator 13: LNG steam pipe 14: heater 15: LNG gas pipe 16: refrigerant pipe 17: refrigerant pipe 18: Refrigerant valve 19: Bypass valve 20: Refrigerant circulation pump 21: Discharge pressure control valve 22: Refrigerant pipe 23A: Refrigerant valve 23B: Refrigerant valve 24: Refrigerant pipe 25: Expansion valve 26C: Evaporator 26D: Evaporator 26E: Evaporation 26H: Evaporator 27: Large compressor 28: Seawater condenser 29: Refrigerant pipe 30: Refrigerant valve 31: Refrigerant pipe 32: Expansion valve 33: Small compressor or fan 34: Refrigerant pipe 35: Heater 36: Expansion valve 37 :Pressure reducing valve 8: refrigerant pipe 39: brine pipe 40A: brine tank A
40B: Brine tank B
41A: Brine pump A
41B: Brine pump B
42: Brine pipe 43: Brine pipe 44: Brine circulation valve 45: Brine pipe 46: Brine flow rate control valve 47: Steam pipe 48: Steam pipe C: Refrigerant supercooling and seawater cooling system with LNG cold, air conditioner room, upper Deck installation D: Refrigerant condensation with LNG cold, small compressor or fan drive system, air conditioning room, upper deck installation E: Refrigerant condensation with LNG cold, pump drive system, air conditioning room, upper deck installation F: LNG cold Recovery system, main engine room, lower deck installation G: brine cold storage system, main engine room, lower deck installation H: air cooling system with cold storage brine, air conditioning room, upper deck installation 49: refrigerant or brine 50: LNG
51: High thermal conductive coating material 52: Low thermal conductive metal outer tube 53: Low thermal conductive metal inner tube 54: Low thermal conductive support material 55: Inert gas or non-flammable heat insulating material

Claims (7)

  Condensation of refrigerant gas and refrigerant directly through a pipe system in a steam-heated LNG heat exchanger using the cold of liquefied natural gas (hereinafter referred to as LNG) as fuel for a propulsion engine (hereinafter referred to as main engine) of the hull The liquid is supercooled, and at the same time, the cold storage agent (hereinafter referred to as the brine) is cooled for the cold storage by surplus cooling heat, and when the cold heat of LNG cannot be obtained, the air is directly cooled by the cold stored brine, Or, it has a function to cool the refrigerant with seawater, and the selection and operation of these functions are switched only by the valve operation of the pipe system, so that there is little cold heat recovery that optimally combines the thermal properties of LNG, brine, and seawater An air conditioning system for ships that is driven by power consumption (hereinafter referred to as an air conditioning system).   Depending on the ratio between the heat load of the air conditioning system and the flow rate of LNG, the use of LNG cold can be switched between condensation of refrigerant gas or supercooling of refrigerant liquid once liquefied with seawater. In the case of supercooling, it is possible to switch between using the LNG's cold heat as the total effective cold quantity of LNG's latent heat and sensible heat, or only sensible heat, depending on the degree of necessity of supercooling. 1 Air conditioning system In parallel with the use of LNG cold energy in the air conditioning system, the brine is cooled to a fixed set temperature with excess LNG cold heat in the same cold heat recovery device and stored in a storage tank, and LNG cannot be obtained The air conditioning system according to claim 1, wherein the brine is supplied from the storage tank to an air cooler to directly cool the air, and the recovered brine is stored in another receiving tank.   In the case of direct air cooling with brine, in order to prevent overcooling of the air due to an excessively low temperature of the brine and moisture condensation in the air, the brine that has been heated after air cooling is mixed with the supply brine at the inlet to adjust to a constant temperature. The air conditioning system according to claim 1 to be supplied   When the refrigerant is liquefied by the cold heat of LNG, the refrigerant circulation system is as follows: (1) The refrigerant vaporized gas from the air-cooled evaporator is boosted by a fan or compressor with a small driving force and sent to the cold heat recovery device of LNG A system that liquefies by the collector and sends the liquefied refrigerant to the expansion valve after adjusting the pressure and flow rate with a small pump, and sends it to the evaporator after decompression, or (2) vaporization of the refrigerant from the evaporator The pressure of the gas is reduced by a pressure reducing valve and sent to a cold energy recovery unit of LNG. The recovery unit liquefies the gas at a lower temperature. The pressure of the liquefied refrigerant is increased by a small pump and the pressure and flow rate are adjusted. An air conditioning system according to claim 1, wherein a system for raising the temperature of the cooling component and sending it to the evaporator via an expansion valve is installed, either of these systems (1) or (2)   The air-conditioning system according to claim 1, further comprising a heat recovery unit for LNG having a heat transfer structure in which a tube surface temperature of the heat exchanger between LNG and the refrigerant or brine is not lowered below the solidification temperature of the refrigerant or brine by an extremely low temperature of LNG.   2. An LNG heat recovery device having a heat transfer mechanism for recovering when the tube surface temperature of the heat exchanger of LNG and refrigerant or brine is locally lowered below the solidification temperature of the refrigerant or brine. Air conditioning system