JP5247519B2 - Absorber - Google Patents

Description

  The present invention relates to an absorber of an absorption chiller / heater, and more particularly, an absorption chiller / heater that can selectively supply cold water that performs a cooling operation such as cooling and hot water that performs a heating operation such as heating. It relates to the absorber of a water machine.

  FIG. 3 shows an example of a dual-effect absorption chiller / heater that circulates and supplies conventional cold water or hot water to a load (see Patent Documents 1 and 2). Water is used as the refrigerant, and an aqueous lithium bromide (LiBr) solution is used as the absorbing solution.

In FIG. 3, 1 is a high temperature regenerator equipped with a gas burner 1B, 2 is a low temperature regenerator, 3 is a condenser, 4 is an evaporator, 5 is an absorber, 6 is a low temperature heat exchanger, 7 is a high temperature heat exchanger, 8 to 11 are absorption liquid pipes, 13 is an absorption liquid pump, 14 to 18 are refrigerant pipes, 19 is a refrigerant pump, 21 is a cold / hot water pipe through which cold water or hot water supplied to a cooling / heating load (not shown) flows, and 22 is cold / hot water. A pump, 23 is a cooling water pipe, 24 is a concentrated absorbent liquid pipe, 25 is a pressure equalizing pipe, 26 to 29 are open / close valves, 40 is a concentrated absorbent spraying apparatus, 41 is a concentrated absorbent pump, and the like.
In the absorber 5, the refrigerant vapor generated and supplied by the evaporator 4 is separated from the refrigerant vapor from the low-temperature regenerator 2, and the concentrated absorption supplied through the absorbent liquid pipe 10 by the operation of the concentrated absorbent pump 41. The liquid is uniformly distributed on the heat transfer pipe 23A of the absorber heat exchanger composed of a plurality of heat transfer pipes (bearing pipes) 23A that are connected to the cooling water pipe 23 by the concentrated absorbent spraying device 40 and into which the cooling water flows. It is sprayed and absorbed to form a rare absorbent, which is supplied to the high temperature regenerator 1. In FIG. 3, C indicates a controller, and 30 indicates a temperature sensor.

  When the absorption chiller / heater is operated, the chilled water cooled by the heat of vaporization of the refrigerant in the heat transfer tube 2 (bare tube) 1A piped inside the evaporator 4 is cooled by the operation of the chilled / hot water pump 22. Since it can be circulated and supplied to a cooling / heating load (not shown) via 21, a cooling operation or the like can be performed.

  However, the conventional absorber heat exchanger composed of a plurality of heat transfer tubes (bare tubes) 23A has low absorption efficiency, and various improvements have been proposed (see Patent Documents 3 to 8).

JP 2000-227263 A Japanese Patent No. 3187878 Japanese Patent Laid-Open No. 10-325643 JP-A-8-247574 JP-A-8-54158 JP-A-6-159862 JP-A-4-369362 JP-A-3-255862

However, these conventional absorber heat exchangers have low absorption efficiency and still have room for improvement.
An object of the present invention is to provide an absorber for an absorption chiller / heater that solves the conventional problems, improves the absorption efficiency of the absorber heat exchanger with a simple new configuration, and also reduces the cost. .

As a result of intensive research conducted by the inventors to solve the above-mentioned problems, the case where only a fin heat transfer tube having an uneven portion such as a fin is used as a heat transfer tube and the case where only a bare heat transfer tube having a smooth surface is used as a heat transfer tube , The heat passage rate K is calculated from the upper side to the lower side using the formula (1) described later from the upper side to the lower side, for example, the vertical axis is the heat passage rate K, and the horizontal axis is [(cooling water Plotting as the difference between (temperature) and (temperature of the concentrated absorbent)] (Δt), the heat transfer rate K of the fin heat transfer tube decreases as Δt decreases, but the heat transfer rate K of the bare heat transfer tube depends on Δt. It has been found that there is a portion where the heat transmission rates K of both coincide with each other since it is not greatly influenced and is almost constant regardless of Δt.
Therefore, the present inventors have found that the above problem can be solved by installing a fin heat transfer tube on the upper side from the above location and connecting and installing the bare heat transfer tube on the lower side from the above location.

The absorber according to claim 1 of the present invention for solving the above problems is a concentrated absorbent spraying device for spraying concentrated absorbent, and an absorber heat exchanger provided below the concentrated absorbent spraying device, The absorber heat exchanger includes a plurality of heat transfer tubes that are connected to a cooling water pipe through which cooling water flows from below to above and from which the concentrated absorbent is sprayed on the outer surface of the pipe. And
For the case where a fin heat transfer tube is used as the heat transfer tube and the case where a bare heat transfer tube is used as the heat transfer tube, find a place where the respective heat transfer rates K calculated by the following equation (1) are equalized, A fin heat transfer tube is installed on the upper side from the location, and a bear heat transfer tube is connected and installed on the lower side from the location.

K = Q / (A × ΔT) (kcal / m ² · ° C. · hr) Formula (1)
Where Q in Equation (1) is the heat exchange amount of the cooling water flowing in the heat transfer tube, A is the heat transfer area of the heat transfer tube, and ΔT is dispersed on the inlet / outlet temperature of the cooling water flowing in the heat transfer tube and the outer surface of the heat transfer tube. Logarithm average temperature difference of the inlet / outlet temperature of the concentrated absorbent, which is determined by the following equations (2) to (5), respectively.

Q (kcal / hr) = (cooling water inlet / outlet temperature difference) × specific heat × cooling water flow rate
Formula (2)

A1 (m ² ) (Bear heat transfer tube heat transfer area) = (Bear heat transfer tube outer diameter × π) × (Bare heat transfer tube length) Formula (3)

A2 (m ² ) (heat transfer area of fin heat transfer tube) = (outer diameter of fin heat transfer tube × π) × (length of bear heat transfer tube) Formula (4)
However, the outer diameter of the fin heat transfer tube in Formula (4) is an average outer diameter before forming irregularities on the outer surface of the tube.

ΔT (° C.) = [(Ta-ta)-(Tb-tb)] / ln [(Ta-ta)-(Tb-tb)] (5)
However, Ta and Tb are the saturation temperature based on the inlet temperature of the concentrated absorption liquid sprayed on the outer surface of the heat transfer tube or the inlet side concentration at the absorber internal pressure, and the outlet temperature or the internal pressure of the absorber, respectively. Represents the saturation temperature based on the outlet side concentration of the water, and ta and tb respectively represent the inlet temperature and the outlet temperature of the cooling water flowing in the heat transfer tube.

  The absorber according to claim 2 of the present invention is the absorber according to claim 1, wherein the fin heat transfer tube is the entire heat transfer tube among the heat transfer tubes composed of the upper heat transfer tubes and the lower heat transfer tubes. Of these, 50% or more.

The concentrated absorbent sprayed on the outer surface of the uppermost tube of the lower heat transfer tube from the concentrated absorbent sprayer provided above the absorber heat exchanger has a high concentration and high temperature, and the inside of the heat transfer tube Although the difference with the temperature of the cooling water flowing upward from below is large, if the refrigerant flows down while absorbing the refrigerant vapor, the concentration of the concentrated absorbent decreases and the difference with the temperature of the cooling water becomes small. Therefore, it is considered that a portion where the heat passage rate K calculated by the above formula (1) becomes uniform appears.
Therefore, the absorber of the present invention finds this place, installs the fin heat transfer tube on the upper side from the location, and installs the bare heat transfer tube having a smooth surface on the lower side from the location, so that the entire heat transfer tube is Compared to the case where it is a bare heat transfer tube or the case where the entire heat transfer tube is a fin heat transfer tube, the absorption efficiency of the absorber heat exchanger is improved, and the outer surface of the tube has a complicated shape. The formed fin heat transfer tube is expensive, and if such complex fins are damaged during handling, the heat transfer rate decreases, whereas the bare heat transfer tube is inexpensive and damages the fins during handling. As a result, it is easy to handle and easy to assemble. As a result, the heat transfer tube can be reduced in cost compared to the case where the entire heat transfer tube is a finned heat transfer tube.

  The absorber according to claim 2 of the present invention is the absorber according to claim 1, wherein the fin heat transfer tube is the entire heat transfer tube among the heat transfer tubes composed of the upper heat transfer tubes and the lower heat transfer tubes. Of these, it is characterized by 50% or more, and has a further remarkable effect that higher absorption efficiency can be obtained as compared with the case where the entire heat transfer tube is a bare heat transfer tube.

It is explanatory drawing explaining an example of the absorber of this invention. The result of calculating the heat transfer rate K for each of the case where only the fin heat transfer tube is used as the heat transfer tube and the case where only the bare heat transfer tube is used as the heat transfer tube (as a ratio (%) to the average heat transfer rate K of the bear tube) Is a graph showing a relationship between [(temperature of cooling water) and (temperature of concentrated absorbent)] (Δt). It is explanatory drawing for demonstrating the example of the conventional absorption cold / hot water machine typically.

Hereinafter, the present invention will be described in detail with reference to the drawings.
FIG. 1 is an explanatory view for explaining an absorber of the present invention.
FIG. 2 shows the results of calculating the heat transfer rate K for the case where only the fin heat transfer tube is used as the heat transfer tube and the case where only the bare heat transfer tube is used as the heat transfer tube (the vertical axis indicates the average heat transfer rate of the bear tube). It is a graph showing the relationship between (the ratio (%) to K) and [difference between (temperature of cooling water) and (temperature of concentrated absorbent)] (Δt).

  When the absorber 5 of the absorption chiller / heater shown in FIG. 3 is used and the fin heat transfer tube (23A-2) having uneven portions such as fins is used as the heat transfer tube 23A, the heat transfer tube 23A has a smooth surface. About the case where a bear heat exchanger tube (23A-3) is used, each heat passage rate K calculated by the previous formula (1) is obtained by an experiment, and the horizontal axis indicates [(cooling water temperature) and (concentrated absorbent liquid FIG. 2 shows the results of plotting the heat transfer rate K (indicated by the ratio (%) to the average heat transfer rate K of the bare tube) on the vertical axis.

  As shown in FIG. 2, a location where the respective heat passage rates K (indicated by a ratio (%) with respect to the average heat passage rate K of the bare tube) intersect is found, so the heat transfer tubes of the absorber 5 corresponding to the locations are found. The location of 23A (the location where the respective heat transfer rates K are equalized, that is, the location of the heat transfer tube 23A-1 in FIG. 1) is specified.

The absorber 5A of the present invention shown in FIG. 1 is provided with a fin heat transfer tube (heat transfer tube 23A-2) having a concavo-convex portion on the upper side from the location, and a bare heat transfer tube having a smooth surface on the lower side from the location. Except that the (heat transfer tube 23A-3) is connected to the fin heat transfer tube (heat transfer tube 23A-2) and installed, it is configured in the same manner as the absorber 5 of the absorption chiller / heater shown in FIG.
In FIG. 1, the same reference numerals as those in FIG. 3 have the same functions as the same reference numerals described in FIG.

In the experiment, an average spraying amount that is normally used is a spraying amount of concentrated absorbent sprayed on the outer surface of the heat transfer tube 23A below from the concentrated absorbent spraying device 40 provided above the absorber heat exchanger. 1.0 L / min · m).
In FIG. 2, in the region where Δt exceeds 4 and 10, the heat transfer rate K (%) of the fin heat transfer tube (23A-2) is larger than the heat transfer rate K (100%) of the bare tube (23A-3). In the vicinity of Δt of 4, both become uniform, and in the region where Δt is less than 4, the heat transfer rate K (%) of the fin heat transfer tube (23A-2) is the heat transfer of the bare tube (23A-3). It became smaller than rate K (100%). Thereby, the location (location of the heat transfer tube 23A-1 in FIG. 1) where the heat transfer rates K of both of them became uniform could be found.

The reason why the heat transfer rate K of the fin heat transfer tube and the heat transfer rate K of the bare tube are reversed by Δt as shown in FIG. 2 is not clear.
However, when Δt is large, it is clear that the heat transfer rate K naturally increases because the fin heat transfer tube has a larger surface area. Usually, in the industry, Δt is increased by using the fin heat transfer tube to increase heat exchange. Getting rate.
Thus, when Δt is large, a large heat transfer rate K is obtained by convection in the liquid film of the fin heat transfer tube, but when Δt is small, convection in the liquid film is not promoted, It is considered that the liquid film becomes an obstacle to heat transfer and the heat transfer rate K decreases.

On the other hand, in the case of a bare heat transfer tube, even if Δt becomes small, the absorbing liquid is drawn by gravity and flows down, so that the absorbing liquid hardly stagnates on the surface, and if the absorbing liquid does not stagnate, the surface area is small. For this reason, it is considered that the heat transfer rate K is maintained without lowering.
Of course, the heat transfer rate K of the fin heat transfer tube and the heat transfer rate K of the bare tube are reversed by Δt is not limited to this idea.

  The fin heat transfer tube used in the present invention may be a heat transfer tube having a concavo-convex portion on the outer surface of the tube, a heat transfer tube having a concavo-convex shape processed on the outer surface of the tube, and specifically, for example, the tube length of the outer surface of the tube Heat transfer tube with concave shape engraved in the hand direction, heat transfer tube with spiral concave shape (low fin shape) engraved in the tube circumferential direction on the outer surface of the tube, floral pattern tube with a cross-sectional floral pattern (commercially available floral pattern tube And the number of grooves is different, or there are many various types). These materials, shapes, dimensions, and the like can be appropriately selected and used in accordance with the capacity and specifications of the absorption chiller / heater.

  The bare tube used in the present invention may be a bare tube having a smooth surface, and specifically includes, for example, a tube having a smooth outer surface (a tube not subjected to processing such as protrusions). be able to. These materials, shapes, dimensions, and the like can be appropriately selected and used in accordance with the capacity and specifications of the absorption chiller / heater.

In the present invention, any combination of the fin heat transfer tube and the bare tube can be used as long as a portion where the heat transfer rates K of both of them are uniform can be found.
The outer diameters of the bare tube and the fin heat transfer tube are both average outer diameters. And since a fin heat exchanger tube uses a bare pipe as a base and forms an unevenness | corrugation in the outer surface and manufactures a fin heat exchanger tube, the part which the unevenness | corrugation is not formed exists in the both ends of the manufactured fin heat exchanger tube. Therefore, the outer diameter of the fin heat transfer tube can be determined from the average outer diameter from both ends. On the other hand, in the case of a finned heat transfer tube where there is no portion with unevenness at both ends, the calculation is based on the distance between the top of the unevenness and the bottom of the recess (valley) formed on the outer surface of the tube. To find the average outer diameter.

  The description of the above embodiment is for explaining the present invention, and does not limit the invention described in the claims or reduce the scope. Moreover, each part structure of this invention is not restricted to the said embodiment, A various deformation | transformation is possible within the technical scope as described in a claim.

  EXAMPLES Hereinafter, although this invention is demonstrated by an Example and a comparative example, unless it deviates from the main point of this invention, this invention is not limited to these Examples.

Example 1
In FIG. 3 provided with the absorber having the configuration of the heat transfer tube shown in FIG. 1, the upper 70% of the heat transfer tubes installed in the absorber 5 are finned heat transfer tubes, and the remaining 30 below. % Of the heat transfer tube is a bear heat transfer tube, the cooling water temperature flowing through the cooling water tube 23 is 32 ° C. at the inlet of the absorber, and 37.5 ° C. at the outlet of the condenser. As a result of the cooling operation with the temperature of the chilled and hot water circulated to the load being 12 ° C. from the load and 7 ° C. from the evaporator 4, it is installed in the absorber 5 as a comparative example. As compared with the case where all the heat transfer tubes are all bare heat transfer tubes or the case where all the heat transfer tubes installed in the absorber 5 are all fin tubes, excellent absorption efficiency can be obtained.

In the first embodiment, 70% of the heat transfer tubes in the upper part of all the heat transfer tubes installed in the absorber 5 are finned heat transfer tubes, but this ratio is not limited to 70%. It can be changed depending on the configuration of the device 5 or the like.
However, the finned heat transfer tube is better when the flow of the absorbing liquid on the surface of the heat transfer tube is performed smoothly, and actually, the range of 50% or more in the upper part of all the heat transfer tubes installed in the absorber. In many cases, the flow of the absorbing liquid on the surface of the heat transfer tube is performed smoothly. Therefore, it is often preferable to use the heat transfer tube as a fin heat transfer tube for 50% or more of the upper part of all the heat transfer tubes.

  The absorber of the present invention finds a place where the heat transfer rate K calculated by the equation (1) becomes uniform, installs a fin heat transfer tube on the upper side of the place, and has a smooth surface on the lower side of the place. Since the bare heat transfer tube has been installed, the absorption efficiency of the absorber heat exchanger is improved compared to the case where the entire heat transfer tube is a bare heat transfer tube or the case where the entire heat transfer tube is a fin heat transfer tube, and the fin Heat transfer tubes are expensive, and if such complex fins are damaged during handling, the heat transfer rate decreases, whereas bare heat transfer tubes are inexpensive and do not damage the fins during handling. Since it has good characteristics and is easy to assemble, the cost can be further reduced. Therefore, the industrial utility value is very large.

DESCRIPTION OF SYMBOLS 1 High temperature regenerator 1B Gas burner 2 Low temperature regenerator 3 Condenser 4 Evaporator 5, 5A Absorber 6 Low temperature heat exchanger 7 High temperature heat exchanger 8-11 Absorption liquid pipe 13 Absorption liquid pump 14-18 Refrigerant pipe 19 Refrigerant pump 21 Chilled / hot water pipe 21A Heat transfer pipe 22 Chilled / hot water pump 23 Cooling water pipe 23A Heat transfer pipe 23A-1 Heat transfer pipe 23A-2 where heat passing rate K is equalized Finned heat transfer pipe 23A-3 Bare heat transfer pipe 24 Concentrated absorption liquid pipe 25 Pressure equalizing pipe 26-29 On-off valve 30 Temperature sensor C Controller 40 Concentrated absorbent spraying device 41 Concentrated absorbent pump

Claims (2)

It is equipped with a concentrated absorbent spraying device that sprays the concentrated absorbent and an absorber heat exchanger provided below the concentrated absorbent spraying device. The absorber heat exchanger circulates cooling water from below to above. A plurality of heat transfer pipes connected to a cooling water pipe to be sprayed on the outer surface of the pipe from the concentrated absorbent spraying device,
For the case where a fin heat transfer tube is used as the heat transfer tube and the case where a bare heat transfer tube is used as the heat transfer tube, find a place where the respective heat transfer rates K calculated by the following equation (1) are equalized, The absorber which installed the fin heat exchanger tube in the upper stage side from the location, and connected the bear heat exchanger tube in the lower step side from the location.
K = Q / (A × ΔT) (kcal / m ² · ° C. · hr) Formula (1)
Where Q in Equation (1) is the heat exchange amount of the cooling water flowing in the heat transfer tube, A is the heat transfer area of the heat transfer tube, and ΔT is dispersed on the inlet / outlet temperature of the cooling water flowing in the heat transfer tube and the outer surface of the heat transfer tube. Logarithm average temperature difference of the inlet / outlet temperature of the concentrated absorbent, which is determined by the following equations (2) to (5), respectively.
Q (kcal / hr) = (cooling water inlet / outlet temperature difference) × specific heat × cooling water flow rate
Formula (2)
A1 (m ² ) (Bear heat transfer tube heat transfer area) = (Bear heat transfer tube outer diameter × π) × (Bare heat transfer tube length) Formula (3)
A2 (m ² ) (heat transfer area of fin heat transfer tube) = (outer diameter of fin heat transfer tube × π) × (length of bear heat transfer tube) Formula (4)
However, the outer diameter of the fin heat transfer tube in Formula (4) is an average outer diameter before forming irregularities on the outer surface of the tube.
ΔT (° C.) = [(Ta-ta)-(Tb-tb)] / ln [(Ta-ta)-(Tb-tb)] (5)
However, Ta and Tb are the saturation temperature based on the inlet temperature of the concentrated absorption liquid sprayed on the outer surface of the heat transfer tube or the inlet side concentration at the absorber internal pressure, and the outlet temperature or the internal pressure of the absorber, respectively. Represents the saturation temperature based on the outlet side concentration of the water, and ta and tb respectively represent the inlet temperature and the outlet temperature of the cooling water flowing in the heat transfer tube.   2. The absorber according to claim 1, wherein the fin heat transfer tube is 50% or more of the heat transfer tube including the upper heat transfer tube and the lower heat transfer tube.

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