Cryogenic pump for liquefied gases

Abstract

A cryogenic pump for liquefied gases is provided, which shortens precooling time, has a small loss of cryogenic liquefied gas, excels in pump efficiency, and is advantageous in cost. A motor 1 and an impeller 2 are coupled by a shaft 3 for transmitting a rotative drive force therebetween, and the motor 1 is arranged on an upper side and the impeller 2 is arranged on a lower side. The motor 1 and the impeller 2 exist in an enclosed space 14 where they are communicated with each other and into which the cryogenic liquefied gas is introduced. A heat adjusting unit 11 is provided between the motor 1 and the impeller 2, the heat adjusting unit maintaining existence of the impeller 2 in a liquid phase of the cryogenic liquefied gas and maintaining existence of the motor 1 in a gas phase of the cryogenic liquefied gas. Thus the submerging of the motor 1 in the liquid becomes unnecessary, whereby the precooling time can be reduced remarkably and the loss of cryogenic liquefied gas due to vaporization caused by the submerging can be reduced, and in addition, the motor 1 itself can be configured at a comparatively low cost.

Claims

1. A cryogenic pump for liquefied gas for applying a pressure difference to the liquefied gas so as to pump-transfer the gas, the cryogenic pump comprising: a motor; and an impeller driven by the motor to cause pump-transfer of the liquefied gas, wherein the motor and the impeller are coupled to each other by a rotation transmitting structure configured for transmitting a rotative drive force therebetween, wherein the motor and the impeller are arranged so that the motor is positioned on an upper side and the impeller is positioned on a lower side, wherein the motor and the impeller exist in an enclosed space into which the liquefied gas is introduced, wherein the enclosed space comprises a space for the motor, a space for the impeller and a space for at least a part of the rotation transmitting structure, wherein the space for the motor is positioned above the space for the impeller, wherein the cryogenic pump further comprises a heat adjusting unit between the motor and the impeller and residing in an atmosphere, wherein the heat adjusting unit comprises a heat adjusting housing that forms the space for the at least part of the rotation transmitting structure, the rotation transmitting structure and heat adjusting unit configured to maintain a temperature in the impeller space in a range in which the liquefied gas is in its liquid phase and to maintain a temperature in the motor space in which the liquefied gas therein is in its gaseous phase, wherein the heat adjusting unit comprises a plurality of fins configured to cause heat to conduct between the atmosphere and rotation transmitting structure through the heat adjusting housing.

2. The cryogenic pump for liquefied gases of claim 1, wherein the rotation transmitting structure comprises at least one shaft provided coaxially to both a rotational axis of the motor and a rotational axis of the impeller.

3. The cryogenic pump for liquefied gases of claim 2, wherein the at least one shaft is supported by a bearing in the motor space within the enclosed space.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a view showing an overall structure of a cryogenic pump for liquefied gases according to a first embodiment of the present invention.

(2) FIG. 2 is a view showing an overall structure of a cryogenic pump for liquefied gases according to a second embodiment.

(3) FIG. 3 is a view showing an overall structure of a cryogenic pump for liquefied gases according to a third embodiment.

(4) FIG. 4 is a schematic view showing a method of an experiment.

(5) FIG. 5 is a graphic chart showing variations of a surface temperature of a SUS304 round bar having the diameter of 10 mm.

(6) FIG. 6 is a graphic chart showing variations of the surface temperature of a SUS304 round bar having the diameter of 20 mm.

(7) FIG. 7 is a graphic chart showing variations of the surface temperature of a SUS304 round bar having the diameter of 30 mm.

(8) FIG. 8 is a graphic chart showing temperature distributions in a temperature stable state according to shaft diameters.

(9) FIG. 9 is a graphic chart showing heat transfer temperature distributions according to the difference of shaft diameters (theoretical calculation value).

(10) FIG. 10 is a graphic chart showing heat transfer temperature distributions according to the difference in thickness of a heat adjusting housing (theoretical calculation value).

MODES FOR CARRYING OUT THE INVENTION

(11) Next, embodiments for carrying out the present invention will be discussed.

(12) FIG. 1 is a schematic view showing a first embodiment of a cryogenic pump for liquefied gases of the present invention.

(13) This is a cryogenic pump for liquefied gases for applying a pressure difference to cryogenic liquefied gas so as to pump-transfer the gas by rotationally driving an impeller 2 by a motor 1.

(14) The motor 1 may be manufactured based on an ordinary motor, for example a DC motor or a three-phase induction motor. Other than this, when a PM motor (permanent magnet motor) is used, the energy efficiency of the pump can improve.

(15) Further, outer walls of the motor 1 are surrounded by pressure-resistance walls 4a and 4b, and an inner space of the pressure-resistance walls 4a and 4b is formed to be a motor space 5 for accommodating the motor 1. A motor unit 20 is formed, including the pressure-resistance walls 4a and 4b and the motor 1 discussed above.

(16) The impeller 2 is positioned in a volute housing 7 communicating with an introduction channel 6 for introducing the cryogenic liquefied gas therein, and is driven rotationally. The rotation of the impeller 2 in the volute housing 7 generates a centrifugal force, and applies the pressure difference to the cryogenic liquefied gas introduced from the introduction channel 6. Then the cryogenic liquefied gas is discharged from a discharge part 8 provided on an outer circumferential part of the volute housing 7. A space inside the volute housing 7 serves as an impeller space 9 accommodating the impeller 2. A reference numeral 10 in FIG. 1 refers to an inducer 10 for facilitating flowage of the cryogenic liquefied gas. A pump unit 19 is formed, including the impeller 2, the volute housing 7 and the inducer 10.

(17) The motor 1 and the impeller 2 are coupled to each other by a rotation transmitting structure/means for transmitting the rotative drive force therebetween. According to the present example, a single common shaft 3 serving as the rotation transmitting means, used coaxially to a rotational axis of the motor 1 and a rotational axis of the impeller 2. Note that, the shaft 3 is not limited to a single type which is commonly used for the motor 1 and the impeller 2, and the shaft for the motor 1 and the shaft for the impeller 2 may be provided separately and coupled by, for example, coupling to each other.

(18) A certain amount of space is secured between the motor 1 and the impeller 2, and a heat adjusting housing 12 covers a part in which the shaft 3 passes through the space. An inner space of the heat adjusting housing 12 is formed to be a shaft space 13 for accommodating the part of the shaft 3.

(19) The motor 1, the impeller 2 and the shaft 3 respectively exist in an enclosed space 14 where they communicate with each other and into which the cryogenic liquefied gas is introduced. According to the present example, the enclosed space 14 is comprised to include the motor space 5, the impeller space 9 and the shaft space 13, respectively forming a part of the enclosed space 14. The shaft space 13 serves as the rotation transmitting means space. The motor space 5, the impeller space 9 and the shaft space 13 communicate with each other. Accordingly, a single pressure-enclosed space is formed by the volute housing 7, the heat adjusting housing 12 and the pressure-resistance walls 4a and 4b of the motor 1.

(20) With reference to the motor 1 and the impeller 2, the motor 1 is positioned on an upper side and the impeller 2 is positioned on a lower side.

(21) Further, a heat adjusting unit 11 between the motor 1 and the impeller 2, for maintaining existence of the impeller 2 in a liquid phase of the cryogenic liquefied gas and also for maintaining existence of the motor 1 in a gas phase of the cryogenic liquefied gas.

(22) The heat adjusting unit 11 has the shaft space 13 and the part of the shaft 3 existing therein. Further, the heat adjusting unit 11 further has the heat adjusting housing 12 for forming the shaft space 13, and fins 15 serving as a heat giving structure/means for giving heat to the heat adjusting housing 12.

(23) As discussed above, the heat adjusting unit 11 is provided in an atmosphere in the space part formed between the motor 1 and the impeller 2. The impeller 2, the heat adjusting unit 11 and the motor 1 are arranged in this order from the lower side. Accordingly, because of the properties that cool air goes down and hot air goes up, the temperature range can be divided effectively, which corresponds to the structural arrangement of the pump, where the impeller 2 in the lower part of the pump is positioned in a cryogenic section, the heat adjusting unit 11 in the intermediate part is positioned in the low/normal-temperature section, and the motor 1 in the upper part is positioned in the normal-temperature section.

(24) Fins on the heat adjusting unit 11 cause heat to conduct between the atmosphere in which the heat adjusting unit 11 resides and the rotation transmitting structure space through the heat adjusting housing 12.

(25) The shaft 3 is pivoted by bearings 16 existing in the gas phase of the enclosed space 14. Thus in the bearings 16, the bearing of the motor 1 is also used as a pump bearing, and the single shaft 3 is used as a pump shaft and also as a motor shaft.

(26) A cooling fan 17 rotationally interlocked with the motor 1 is arranged above the motor 1, for cooling the motor 1. The reference numeral 18 in FIG. 1 refers to a fan cover 18.

(27) With such a structure, the cryogenic liquefied gas is sucked into the pump from the part with the inducer 10 at the bottom of FIG. 1, and is given a moving force by the impeller 2, and is discharged from the discharge part 8. Once the cryogenic liquefied gas enters the inside of the pump, there is no outlet but only the discharge part, and the cryogenic liquefied gas will not move towards the motor 1 because of the dead-end structure of the enclosed space 14.

(28) Thus, because of the property of natural heat convection that cool air goes down and hot air goes up, and also because the cryogenic liquefied gas does not move towards the motor 1, for example, it can be divided that the pump structural part including the lower part impeller 2 as the cryogenic section, the heat adjusting unit 11 in the intermediate part as the low/normal-temperature section, and the part of the motor 1 in the upper part as the normal-temperature section.

(29) Accordingly, the cryogenic liquefied gas is introduced from the introduction channel 6 and flows towards the discharge part 8, and the impeller space 9 for accommodating the impeller 2 is filled with the cryogenic liquefied gas. For example, the gas is kept at the temperature of 150 C. or lower, and is maintained in the liquid phase state. On the other hand, the motor space 5 for accommodating the motor 1 is kept at around the normal temperature, for example at 20 C. or higher, and therefore is filled with the vaporized gas of the cryogenic liquefied gas, whereby the gas phase state is maintained. The temperature of the shaft space 13 is within an intermediate range between the temperature of the motor space 5 and the temperature of the impeller space 9, and a temperature gradient is formed therein.

(30) The section filled with the liquid phase corresponds to that from the introducing channel 6 to the pump unit 19. In particular, the liquid phase section corresponds to that of minimum essential parts only, such as the volute housing 7, a bottom part of the heat adjusting housing 12, the impeller 2, the part of the shaft 3 and the inducer 10. The pump unit 19 is arranged in the lower area, and the section filled with the liquid phase is limited up to the pump unit 19. Consequently, a liquid level in the pump may be lowered to be the level of the discharge part 8.

(31) As discussed above, the space between the motor 1 and the impeller 2, in which the heat adjusting unit 11 is formed, is set so that the motor 1 can be maintained in the gas phase, and the impeller 2 can be maintained in the liquid phase. This is set arbitrarily according to several factors, for example, the diameter of the shaft 3, the thickness of the heat adjusting housing 12, the type of the respective materials, etc.

(32) For example, when the type of material is SUS304, the atmosphere temperature is 20 C., the cryogenic liquefied gas is liquid nitrogen, and the temperature of the motor unit 20 is 5 C. or higher, and further, provided that the diameter of the shaft 3 is 30 mm, then the distance of the heat adjusting unit 11 may be 300 mm or more, and the thickness of the heat adjusting housing 12 here may be 15 mm or less.

(33) The appropriate length of the heat adjusting unit 11 leads to appropriate setting of the length of the shaft 3 and also the length of the heat adjusting housing 12, corresponding to the heat adjusting unit 11. Through theoretical calculation and experiments, it is possible to obtain, for example, the length, the diameter of the shaft 3, the thickness of the heat adjusting housing 12, by which an inlet of the motor unit 20 becomes an appropriate set temperature.

(34) As discussed above, according to the present embodiment, for the purpose of eliminating the conventional shaft seal, the inside of the motor unit 20 and the inside of the pump unit 19 form the enclosed space 14 where they are communicated with each other, and thus the shaft 3 does not penetrate into the atmosphere. For this purpose, the pressure-resistance walls 4a and 4b serve as the outer walls of the motor unit 20.

(35) Moreover, the pump is installed in the upright direction, and the appropriate heat adjusting unit 11 divides the sections into the liquid phase section and the gas phase section, whereby the bearing 16 in the motor 1 are kept at the normal temperature (in this context, normal temperature means a usage environment temperature of common motors, which is approximately between 20 C. and 40 C.). Accordingly, the bearing 16 will not become in direct contact with the cryogenic liquefied gas, and therefore, for example, a low cost bearing made of iron for which common grease is used as the lubricant may be used.

(36) Further, the motor unit 20 will not be in direct contact with the cryogenic liquefied gas, and therefore a common and low cost iron material may be used. The cooling fan 17 interlocked with the motor 1 cools down the heat of the motor unit 20. Moreover, the pressure-resistance walls 4a and 4b serve as the outer walls of the motor unit 20, and accordingly, there is no metal bulkhead between driver magnets, which would be the cause of eddy current.

(37) Further, the cryogenic liquid phase section corresponds only to the pump unit 19, and thus the mass of the structural members with which the cryogenic liquefied gas becomes in contact has been reduced to the least possible. Out of specific major members, the cryogenic liquefied gas becomes in contact with only the volute housing 7, the bottom part of the heat adjusting housing 12, the inducer 10, the impeller 2 and the tip of the shaft 3.

(38) The pump is installed in the upright direction, and the appropriate heat adjusting unit 11 divides the pump into the liquid phase section at the cryogenic and the gas phase section at the normal temperature. Thus the bearing 16 in the motor 1 will not be affected by the cooling of the pump.

(39) Further, the liquid level of the cryogenic liquefied gas entering the inside of the pump is lowered down to the level of the discharge part 8. Further, to form the pressure-resistance structure for the outer walls of the motor 1, the thickness is set to a required thickness that can bear a design pressure, or thicker, that is, a minimum thickness of or thicker than that prescribed by High Pressure Gas Safety Law. Moreover, the same shaft 3 is used for the motor 1 and the impeller 2, and the shaft 3 is supported only by the bearings 16 in the motor 1.

(40) In detail, a seal material, such as gasket or O-ring, is used for each of joint parts of the pressure-resistance walls 4a and 4b of the motor unit 20, the volute housing 7 and the heat adjusting housing 12, and an enclosure structure is secured by fastening flanges by bolts, or by fastening with a screw-thread structure.

(41) As discussed above, according to the cryogenic pump for liquefied gases of the present embodiment, there are following effects.

(42) The inside of the pump unit 19, the inside of the heat adjusting unit 11 and the inside of the motor unit 20 form the enclosed space 14 where they communicate with each other. Thus there is no part in which the shaft penetrates through the atmosphere, and consequently the shaft seal is not required.

(43) The motor unit 20, the appropriate heat adjusting unit 11 and the pump unit 19 are arranged in this order, in the upright direction from the upper part. Therefore the motor unit 20 and the bearing 16 can be kept, for example, at the normal temperature, and the motor 1 and the bearing 16 may be made of ordinary material such as iron steel. Further, a common lubricant, such as grease, may be used for the bearing 16.

(44) The motor unit 20, the appropriate heat adjusting unit 11 and the pump unit 19 are arranged in this order, in the upright direction from the upper part. Therefore the motor unit 20 and the bearing 16 may be kept, for example at the normal temperature, and the heat generated therefrom will not be absorbed directly in the cryogenic liquefied gas. Consequently the amount of lost vaporized gas can be reduced.

(45) The motor unit 20, the appropriate heat adjusting unit 11 and the pump unit 19 are arranged in this order, in the upright direction from the upper part. Further, the motor unit 20 is enclosed. Therefore the liquid level of the cryogenic liquefied gas in the pump is limited to the level of the discharge part 8, and only the pump unit 19 can become the cryogenic liquid phase section. Accordingly, the major structural members of the pump which become in contact with the cryogenic liquefied gas are minimized to the volute housing 7, the bottom part of the heat adjusting housing 12, the inducer 10, the impeller 2 and the tip of the shaft 3. Thus the loss of vaporized gas generated during precooling of the pump may be reduced, and the precooling time may be shortened. Further, since the liquid level of the entering cryogenic liquefied gas may be lowered, the lower limit of the liquid level of the suction-side tank may also be lowered.

(46) Because of the appropriate of heat adjusting unit 11, the pump unit 19 can exist in the liquid phase at the low temperature, and the motor unit 20 may exist in the gas phase, for example at the normal temperature.

(47) FIG. 2 illustrates a second embodiment of the present invention.

(48) According to this example, the motor unit 20 is not provided with the pressure-resistance walls 4a and 4b. Thus, the motor 1 is covered by outer walls 21a and 21b having no pressure-resistance structure, and thus the motor unit 20 is configured. The outside of the motor unit 20 is covered by separate pressure walls 22a and 22b. Other structure is similar to that of the first embodiment, and the same reference numerals are allotted to the similar parts. This example also has similar functions and effects as those of the first embodiment.

(49) FIG. 3 illustrates a third embodiment of the present invention.

(50) According to this example, a fan 24 positioned outside of the motor unit 20 is driven by magnet-coupling for cooling the motor 1. Thus, a part of the shaft 3 on the side of the motor 1 penetrates through the pressure-resistance wall 4b and projecting to the outside, and an inner magnet 25 is attached to the projecting part of the shaft 3. A pressure-resistance cover 26 covers to enclose the space around the inner magnet 25, and the fan 24 provided with an outer magnet 27 is arranged outside of the pressure-resistance cover 26. Other structure is similar to that of the first embodiment, and the same reference numerals are allotted to the similar parts. This example also has similar functions and effects as those of the first embodiment.

(51) Note that, the cooling of the motor 1 may also be carried out, for example, by using a separately-placed cooling fan interlocked with the motor, using a cooling fan installed separately, or applying cooling by water.

(52) According to each embodiment as discussed above, the length of the heat adjusting unit 11 can be shortened by heating the heat adjusting unit 11 or the motor unit 20 by the heat giving means, etc. In addition, when any material having low heat conductivity is used wholly or partially, the length of the heat adjusting unit 11 can be shortened. Also these cases can have similar functions and effects.

(53) According to each embodiment as discussed above, the examples that one or two shafts are used as the rotation transmitting means are discussed. However, the present invention is not limited to these examples, and any other means may be used as long as the rotation of the motor 1 is transmitted to the impeller 2. For example, the shaft for the motor 1 and the shaft for the impeller 2 may be coupled by gear, chain or belt, so that the rotation is transmitted to each other.

(54) Next the appropriate length (distance) of the heat adjusting unit 11 will be discussed.

(55) The appropriate length of the heat adjusting unit 11 is determined by appropriately sets the length of the shaft 3 and also the length of the heat adjusting housing 12, corresponding to the heat adjusting unit 11. Through theoretical calculation and experiments, it is possible to obtain, for example, the length, the diameter of the shaft 3, the thickness of the heat adjusting housing 12, by which the inlet of the motor unit 20 becomes an appropriate set temperature.

(56) For the purpose of determining the appropriate length of the heat adjusting unit 11 for dividing the sections into the liquid phase at the low temperature and the gas phase at the normal temperature, a temperature distribution experiment of the shaft 3 is conducted. The result will be discussed in detail as below with reference to Table 1. In relation to the diameter of the shaft 3, a necessary distance from the surface of liquid nitrogen is obtained at a temperature range between 30 C. and 10 C.

(57) The experiment is conducted with regard to the temperature variation according to the shaft diameter and heat transfer in a state that the tip of the shaft 3 is submerged in the liquid nitrogen, and with regard to the temperature distribution in a temperature stable state in relation to the diameter of the shaft 3.

(58) (Experiment Conditions)

(59) Pump Shaft: SUS304 round bars having the same material property are used. Shaft Diameter: diameter 10 mm, 20 mm and 30 mm are used. Atmosphere Temperature: room temperature (between 20 and 22 C.) Atmosphere Environment: natural convection state Outside Temperature: 20 C.
(Measurement Device) Temperature Measurement and Recording: Portable Multi-Logger ZR-RX40 (manufactured by OMRON) Thermocouple: K-type thermocouple
(Experiment Method)

(60) FIG. 4 is a schematic view showing a method of the experiment. (1) On each of the SUS304 round bars having the diameter of 10 mm, 20 mm and 30 mm, respectively, thermocouples are attached to positions at 0.15 m, 0.20 m, 0.25 m 0.30 m, 0.35 m, 0.40 m, 0.45 m, 0.50 m, 0.55 m and 0.60 m, respectively from a lower tip of the SUS304 round bar. (2) The SUS304 round bar is submerged in the liquid nitrogen by 0.10 m from the tip. The liquid nitrogen is supplemented constantly so that the surface of liquid nitrogen is at the position of 0.10 m from the tip of the round bar. (3) The temperature is measured and recorded, starting from the time immediately after the submerging in the liquid nitrogen. The measurement is conducted at the positions of 50 mm to 500 mm from the surface of liquid nitrogen, at intervals of 50 mm.
(Measurement Result)

(61) FIG. 5 shows the variations of surface temperature of the SUS304 round bar having the diameter of 10 mm (at the respective distances from the liquid surface).

(62) FIG. 6 shows the variations of surface temperature of the SUS304 round bar having the diameter of 20 mm (at the respective distances from the liquid surface).

(63) FIG. 7 shows the variations of surface temperature of the SUS304 round bar having the diameter of 30 mm (at the respective distances from the liquid surface).

(64) (Summary of Temperature Variation According to Shaft Diameter and Heat Transfer)

(65) With regard to the SUS304 round bar of which the diameter is 10 mm, the temperature variation became stable at about 40 minutes after starting the experiment.

(66) With regard to the SUS304 round bar of which the diameter is 20 mm, the temperature variation become stable, about 100 minutes after starting the experiment.

(67) With regard to the SUS304 round bar of which the diameter is 30 mm, the temperature variation become stable, about 150 minutes after starting the experiment.

(68) FIG. 8 is a graphic chart showing the temperature distribution in the temperature stable state according to the shaft diameters.

(69) In accordance with the experiment result and with consideration of some tolerance, a temperature stabilizing time for all of the shaft diameters is estimated as 170 minutes after starting the experiment, and the graphic chart is prepared with regard to the temperature distribution in the temperature stable state.

(70) Table 1 summarizes the relation between the stabled temperature and the distance from the surface of liquid nitrogen according to the respective shaft diameters, analyzed from the graphic chart.

(71) TABLE-US-00001 TABLE 1 Stabled Distance from Surface of Liquid Nitrogen (mm) Temperature Shaft Diameter Shaft Diameter Shaft Diameter ( C.) 10 mm 20 mm 30 mm 30 45 77 110 20 50 93 131 10 55 112 158 0 73 145 190 10 100 195 246

(72) Next, the temperature distribution of the shaft and the temperature adjusting housing 12 is also discussed by theoretical calculation.

(73) First, the temperature distribution of the pump shaft is calculated.

(74) (1) A surface heat transfer rate by the natural convection is calculated (refer to the calculation formula of vertical plane and tube, JIS A 9501 2001 5.3.3 (2))

(75) <Formula>
hcv=2.56^0.25{(+0.3438)/0.348}^0.5 hcv: surface heat transfer rate by convection (W/(m.sup.2.Math.K)) : temperature difference (K) (calculated with the liquid nitrogen temperature as 77K, the room temperature as 293K) : wind velocity (m/s) (calculated as 0 m/s under natural convection)
<Calculation>

(76) $\begin{array}{c}\mathrm{hcv}=2.56(293-77^0.25\left\{\left(0+0.3438\right)/0.348\right\}^0.5\\ =9.814\left(W\text{/}{m}^2.Math.K\right))\end{array}$
2) Simplified Temperature Distribution Calculation

(77) The simplified temperature distribution is calculated by utilizing the result of (1) (Fundamental Study of Heat Transfer by Suguru YOSHIDA, Rikogakusha Publishing Co., Ltd., p. 36-39 (1999)).

(78) <Presumption>

(79) The temperature on a cross-sectional surface perpendicular to the shaft is uniform. A heat transfer rate from the surface to the circumferential fluid (temperature: Tb) (hcv of the above calculated value) is uniform for the whole surface. A cross-sectional area A and a circumferential length S are constant in the axial direction. A heat conductivity is constant.
<Calculation Conditions>

(80) Overall Length H=0.5 m

(81) Liquid Nitrogen Temperature T0=77K

(82) Room Temperature Tb=293K

(83) Heat Transfer rate =9.814 (the calculated value of (1))

(84) Shaft Diameter =30 mm (material: SUS304)

(85) Shaft Circumferential Length S=0.0942 m

(86) Shaft Cross-sectional Area A=7.06510.sup.4

(87) SUS304 Heat Conductivity (room temperature: 293K) =15.9 W/(m.Math.K)

(88) (New Edition of Thermophysical Properties Handbook edited by Japan Society of Thermophysical Properties, Yokendo Co., Ltd., p. 213 (2008))

(89) <Calculation>

(90) (x refers to the distance from the liquid surface to the temperature measurement point (m), and T refers to the temperature at the distance point).
m=((S)/(A))^0.5 m.sup.1(based on Formula 2.73)
Temperature Distribution =(e^(m(Hx))+e^(m(Hx)/e^(mH)+e^(mH)(based on Formula 2.79)
=(TTb)/(T0Tb)(based on Formula 2.72)

(91) The above formulas are solved and the simplified temperature distribution is obtained.

(92) <Calculation Result>

(93) TABLE-US-00002 TABLE 2 x(m) T(K) 0.00 1.0000 77 0.05 0.6355 156 0.10 0.4039 206 0.15 0.2569 238 0.20 0.1636 258 0.25 0.1046 270 0.30 0.0675 278 0.35 0.0445 283 0.40 0.0309 286 0.45 0.0237 288 0.50 0.0214 288
(3) Temperature Amendment According to the Simplified Temperature Distribution. (A) A surface heat transfer rate by radiation at each of the calculation points is obtained, according to the temperature obtained by the simplified temperature distribution of (2). Then the calculation value of (1) is combined thereto to obtain a surface heat transfer rate (refer to JIS A 9501 2001 5.3.3 (1)).
hr=arCr(W/m.sup.2K))
ar=((Tse).sup.4(Ta).sup.4/(TseTa)(K.sup.3)
Cr=.Math.(W/m.sup.2.Math.K.sup.4)) hr: surface heat transfer rate by radiation (W/(m.sup.2K) Tse: temperature (K) at each of the distances obtained by the calculation of (2) Ta: room temperature (293K) : 0.30 (using the value of stainless steel panel) : Stefan-Boltzmann constant 5.6710^8(W/m^2.Math.K^4) Surface Heat Transfer Rate (hse) (refer to JIS A 9501 2001 5.3.3)
hse=hr+hcv
<Calculation Result>

(94) TABLE-US-00003 TABLE 3 x(m) hr(W/(m.sup.2 .Math. K) hse(W/(m.sup.2 .Math. K) 0.00 0.578 10.392 0.05 0.840 10.654 0.10 1.088 10.902 0.15 1.284 11.098 0.20 1.426 11.240 0.25 1.523 11.337 0.30 1.588 11.402 0.35 1.629 11.443 0.40 1.654 11.468 0.45 1.667 11.481 0.50 1.671 11.485 (B) The heat conductivity at each of the calculation points is obtained, according to the temperature obtained by the simplified temperature distribution of (2).

(95) For the purpose of obtaining the heat conductivities of SUS at the respective temperatures, the heat conductivities at 60K and 100K are read from the heat conductivity graphic chart of various materials at T>1K, in accordance with Low-Temperature Engineering Handbook supervised by Toyoichiro SHIGI, Uchida Rokakuho Publishing Co., Ltd., p. 197 (1982). Then an approximate linear functional equation between 60K-100K, and an approximate linear functional equation between 100K-293K are derived according to the heat conductivity used in the calculation of (2), to serve as the heat conductivity at each of the calculation points.

(96) <Calculation Result>(the heat conductivity at the Temperature T of each point x is 2).

(97) TABLE-US-00004 TABLE 4 x(m) T(K) 2(W/(m .Math. K) 0.00 77 8.3 0.05 156 11.7 0.10 206 13.2 0.15 238 14.2 0.20 258 14.8 0.25 270 15.2 0.30 278 15.5 0.35 283 15.6 0.40 286 15.7 0.45 288 15.7 0.50 288 15.8

(98) Provided that the calculated value of (A) above is , and the calculated value of (B) is , the calculation of (2) is conducted again in order to obtain the temperature distribution value by calculation.

(99) <Calculation Conditions>

(100) Overall Length H=0.5 m

(101) Liquid Nitrogen Temperature T0=77K

(102) Room Temperature Tb=293K

(103) Surface Heat Transfer rate =value of hse obtained by (A)

(104) Shaft Diameter =30 mm (material: SUS304)

(105) Shaft Circumferential Length S=0.0942 m

(106) Shaft Cross-sectional Area A=7.06510.sup.4

(107) SUS304 Heat Conductivity =The value of 2 obtained by the calculation of (B), W/(m.Math.K)

(108) <Calculation>

(109) (x refers to the distance from the liquid surface to the temperature measurement point (m), and T2 refers to the temperature at the distance point).
m=((S)/(A))^0.5 m.sup.1(based on Formula 2.73)
Temperature Distribution 2=(e^(m(Hx)+e^(m(Hx)/(e^(mH)+e^(mH)(based on Formula 2.79)
2=(TTb)/(T0Tb)(based on Formula 2.72)

(110) The above formulas are solved and the temperature distribution is obtained.

(111) <Calculation Result>

(112) TABLE-US-00005 TABLE 5 x(m) 2 T2(K) 0.00 1.0000 77 0.05 0.5765 168 0.10 0.3507 217 0.15 0.2165 246 0.20 0.1341 264 0.25 0.0833 275 0.30 0.0520 282 0.35 0.0330 286 0.40 0.0220 288 0.45 0.0162 289 0.50 0.0145 290 (4) In the case that the pump shaft diameter is 10 mm or 20 mm, when the calculations of (1) to (3) are also conducted, the result as shown in FIG. 9 is obtained. Table 6 shows typical read values of temperature and the distance from the surface of liquid nitrogen.
<Calculation Result>

(113) TABLE-US-00006 TABLE 6 Stabled Distance from Surface of Liquid Nitrogen (mm) Temperature Shaft Diameter Shaft Diameter Shaft Diameter ( C.) 10 mm 20 mm 30 mm 30 85 115 145 20 95 135 170 10 110 160 195 0 135 195 240 10 180 250 310
(Temperature Distribution Calculation of the Heat Adjusting Housing)

(114) In a similar concept to that of the pump shaft, when the temperature distribution according to the difference in thickness of the heat adjusting housing (material: SUS304) is obtained, the result comes out as FIG. 10 (calculated according to the calculations (1) to (4) as described above). Note that the calculation is conducted with the inner diameter of the heat adjusting housing as 100 mm.

(115) As it is clear from the results of these experiments and theoretical calculations, both the actual measured value and the theoretical value show the similar result aspects. It is clear that the present invention has the sufficient industrial applicability when the shaft and the heat adjusting housing are designed in accordance with these results.

DESCRIPTION OF REFERENCE NUMERALS

(116) 1: Motor

(117) 2: Impeller

(118) 3: Shaft

(119) 4a: Pressure-resistance wall

(120) 4b: Pressure-resistance wall

(121) 5: Motor space

(122) 6: Introduction Channel

(123) 7: Volute Housing

(124) 8: Discharge Part

(125) 9: Impeller Space

(126) 10: Inducer

(127) 11: Heat Adjusting unit

(128) 12: Heat Adjusting Housing

(129) 13: Shaft Space

(130) 14: Enclosed Space

(131) 15: Fin

(132) 16: Bearing

(133) 17: Cooling fan

(134) 18: Fan Cover

(135) 19: Pump unit

(136) 20: Motor unit

(137) 21a: Outer Wall

(138) 21b: Outer Wall

(139) 22a: Pressure Wall

(140) 22b: Pressure Wall

(141) 24: Fan

(142) 25: Inner Magnet

(143) 26: Pressure-resistance Cover

(144) 27: Outer Magnet