JP2893459B2 - Air conditioning method using latent heat of water evaporation - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to air conditioning for keeping the temperature and humidity of air in living spaces and various working spaces in an appropriate range mainly in summer, and as a main energy source. Use combustion gas of various fuels and high temperature waste gas.

[Prior art] In a normal living space atmosphere in summer, for example, a temperature of 26 ° C., a relative humidity (hereinafter referred to as RH) of 50%, and an absolute humidity (hereinafter referred to as “humidity”) of around 0.0105 [kg moisture / kg dry air] Is appropriate.

On the other hand, in the summer, the air taken in for ventilation from outside in the daytime is generally hotter and humid. In addition, since sensible heat invades from the roof and walls of the building, etc., and the sensible heat generated inside and the latent heat of evaporated water are constantly applied, circulating these sensible heat and latent heat to obtain the above-mentioned comfortable atmosphere Must be removed from air. In order to remove such sensible heat, cold water of about 5 to 10 ° C. usually obtained by a refrigerator is sent to the low temperature side of the heat exchanger, and circulating air passing through the high temperature side through the heat transfer surface is cooled to 15 ° C. After cooling back and forth, they are returned to the room. Also use a heat exchanger to remove latent heat, that is, moisture,
It is customary to directly contact cold water and lower the air temperature to near the dew point temperature corresponding to the desired humidity to condense and remove the water content. As such a refrigerator, besides a refrigeration system using mechanical energy for obtaining a low temperature by a refrigeration cycle consisting of liquefaction and evaporation of a refrigerant such as freon, a partial absorption refrigerator is known.

In this method, a refrigeration cycle is constructed by utilizing the property that the water vapor pressure of an aqueous solution such as lithium bromide (LiBr) changes depending on the concentration and temperature of the solution.

In the absorption refrigeration system, this aqueous solution is referred to as a working fluid, and a heat source such as a combustion gas, steam, or hot water is used as a main energy source in order to concentrate and reuse a used diluted working fluid.

[Problems to be Solved by the Invention] Demand for electric power for cooling consumed in the summertime in the recent days is rapidly increasing, and each electric power company is required to reinforce the equipment at this time. For this reason, the operation rate of the facilities has to be reduced throughout the year. On the other hand, city gas or petroleum companies have a problem that a portion of the demand that is consumed in large quantities for heating in winter disappears in summer and the operation rate of the equipment is reduced at that time.

In order to solve such an imbalance in seasonal energy supply and demand, cooling equipment using the absorption refrigerator using fuel as an energy source has recently become widespread. According to this, power consumption for cooling requires only a small amount for driving a pump, a blower, and the like, and is excellent in principle in resolving the contradiction as described above.

One disadvantage of this approach is the complexity of the equipment. After changing the combustion gas of the fuel to steam or hot water using a boiler, etc.
It takes more than two places. In the meantime, evaporation and condensation of the diluted working fluid, condensation of the generated steam, and evaporation of water under reduced pressure and absorption of the generated steam into the concentrated working fluid must all be performed under reduced pressure in order to obtain cold heat. There is. Sufficient attention must be paid to the operation of the heat exchanger which may prevent the precipitation of salts from the working fluid and corrode the material, and maintenance and inspection are not easy.

In addition, absorption chiller method first makes cold water around 10 ° C,
In order to cool the air using this, an additional heat exchanger is required.In this case, if the air is to be simultaneously dehumidified, part or all of the air is cooled to a dew point corresponding to the required humidity. Therefore, after condensing and removing excess moisture, it is necessary to further adjust the temperature to a predetermined condition and return it to the original room, which further complicates the system.

As described above, since the entire system is complicated, the equipment cost is relatively high. In addition, due to the structure of the apparatus, there is an upper limit to the equipment capacity per unit.

[Means for Solving the Problems] The present invention is the same as a conventional absorption refrigerator in that it utilizes the property that the water vapor pressure of an aqueous solution of LiBr or the like greatly changes depending on the concentration and temperature of the solute. The fundamental difference is that the incoming air is brought into direct contact with these aqueous solutions to dehumidify it, cooled to around 20 ° C by a special heat exchange method as described below, and then brought into contact with water. The point is to use means for performing adiabatic evaporation to obtain return air at a predetermined temperature and humidity. All of these operations can be performed at 50 ° C. or lower under normal pressure, and have the advantage that only one or two heat exchangers are required. Instead of converting the high-temperature combustion gas into steam or hot water using a boiler or the like and then concentrating the working fluid, the high-temperature gas can be directly brought into contact with the working gas under normal pressure to perform the operation.

In this way the whole system is very simple,
Equipment costs may also be low, regardless of the size.

The operation is simple under normal pressure, and the maintenance and inspection of the equipment can be easily performed.

However, when applied to actual conditions, this method proved to be problematic.

In other words, as described above, indoor air during summer
In order to keep the temperature at ℃ and the humidity at 0.0105 [kg / kg], the returned air should be lower, for example, the temperature at 14 ℃ and the humidity at 0.0080 [kg / kg]
It is said that it is necessary to adjust to the vicinity and blow it into the room.
This condition is on the adiabatic cooling line passing about 12 ° C. at the wet bulb temperature in the psychrometric chart of FIG. 2 described later.

On the other hand, in the same time zone, the outdoor air
If it is 0 [kg / kg], the temperature of the cooling water obtained by the cooling tower under that condition is practically about 32 ° C.

Therefore, the practical limit of indirect cooling of the dry air obtained in the process with the cooling water at this temperature will be about 37 ° C.

Even when the humidity is 0, the wet bulb temperature that can be reached from the air having such a dry bulb temperature is about 13 ° C. when viewed from the adiabatic cooling line, and does not reach the wet bulb temperature. As described later, Li
The humidity of dry air obtained by contact with Br aqueous solution is practically 0.
[0050] Since it is considered to be about [kg / kg], unless this is cooled to about 21 ° C, it will not be placed on the adiabatic cooling line passing through the wet bulb temperature of 12 ° C, and thus the return air as described above cannot be obtained.

As long as the cooling water of 32 ° C. is used, it is almost impossible to cool the air to the above-mentioned 21 ° C. by the indirect cooling method, and therefore, there is no possibility of performing the cooling by such a method.

In the present invention, a part of the return air is returned to the low temperature side of the heat exchanger, and the heat is exchanged by flowing in a counterflow with the dry air on the high temperature side. When the temperature is lowered to near the wet-bulb temperature, the exhaust gas is exhausted after maintaining a sufficient temperature difference from the high-temperature side. By setting the reflux amount to 15-20% of the total, the outlet air temperature on the high-temperature side
It was found that the temperature can be lowered to around 20 ° C. If such water injection is not performed, the amount of reflux will need to be close to 100%, and it will be difficult to secure return air.

In addition, the recirculation ratio required for such exhaust generally matches the intake ratio from the outside for indoor ventilation with respect to the whole received air, so that air to be discarded outdoors for ventilation will be used. Above all, there is no loss.

[Operation] An example of the operation of the present invention will be described with reference to FIG.

The incoming air 1 is sent to an air dehumidification tower 3 by a blower 2. In No. 1, fresh air outside is usually mixed with indoor air at a certain ratio, for example, about 15 to 20% for ventilation. A cooling pipe 5 for a filler layer 4 and cooling water 6 is built in the center of 3. As the incoming air rises inside 4, a thick absorbing solution 7 of LiBr is irrigated from the top of 3 and 4
Comes in contact with rising air while descending. At this contact interface, the moisture in the air moves to the absorbing liquid, but at the same time heat transfer occurs due to the temperature difference between the gas and liquid. At this time, the temperature rise of the liquid due to the heat of absorption and condensation of the water hinders the absorption of water, and thus is appropriately removed by the cooling pipe 5.

The diluted absorption liquid 8 thus absorbed is taken from the bottom of the column and air is taken from the top of the column, for example, at a temperature of 40 ° C. and a humidity of 0.0050 [kg / kg].
Dehumidify and dry to the extent and discharge.

The dry air thus obtained passes through an air cooler 9 containing a cooling pipe 10 and may be appropriately pre-cooled by cooling water 11 in some cases. Also sometimes said from the room
It is also effective to exchange heat with air around 26 ° C.

Next, the dried air is heated to a predetermined temperature in the air heat exchanger 12.
Cool to around 20 ° C.

12 is arranged vertically as shown in the figure, and the inside is divided into a high temperature section 12h and a low temperature section 12c by a partition wall, and a heat transfer mechanism 1 is provided between the two.
The heat transfer due to the temperature difference takes place via 3. Although the figure assumes a heat pipe group with fins, other heat transfer methods in which the air on both sides are not substantially mixed can be used.

The dry air is cooled as it passes from bottom to top for 12 h and reaches, for example, 20 ° C. and subsequently to an adiabatic water evaporator 14. Here, air is injected through a spray nozzle 16 at an appropriate amount near normal temperature.
15 and adiabatic cooling and humidification of air by evaporation of water are performed simultaneously to reach a predetermined temperature and humidity.

For example, if the conditions of the 14 inlet air are as described above, and the water injection amount is about 0.25% by weight of the dry air amount, all the water evaporates to obtain air at a temperature of 14 ° C. and a humidity of about 0.008 [kg / kg]. be able to. This is a satisfactory condition for returning air to the room as described above.

The air that has exited 14 is about 15-20% by the air distribution valve 17.
Is returned to 12 as return air 19, and the remainder is returned to the room as return air 18.

19 is guided to the upper part of the heat exchanger low temperature section 12c, and flows down in the counter current with the high temperature air flow of 12h.

At that time, water was supplied from the upper part of 12h through the water injection nozzle 20 to 17
Is dispersed in the air stream. Although the contact between water and air is sufficiently performed on the surface of the fins 13, a filler or the like may be appropriately disposed around the fins 13 to further increase the contact effect.

Inside 12c, adiabatic cooling and humidification of air are always performed by evaporation of water along the air flow.

As the temperature condition, first, at the inlet of 12c, the temperature of 17 is reduced to around 12 ° C., so that a sufficient temperature difference is obtained to obtain the outlet side temperature of 20 ° C. of 12h. Further 12c
The air passing through the heater receives heat from the 12h side through 13 and heats up, but the water that coexists and contacts it evaporates in proportion to it, so the air always keeps near the wet bulb temperature. Warm up.

The air that has exited from the bottom of 12c separates the excess water flow in the separation tank 21 and is discharged out of the system as discharged air 24.

In 21, supplementary water 23 corresponding to the evaporated water is added, and is sent again to circulation 20 through circulation pump 22 as circulation water.

Next, the concentration and regeneration of the dilution absorbent 8 discharged from the air dehumidification tower 3 will be described.

This concentrating method naturally depends on the type of thermal energy used.

FIG. 1 assumes the use of fluid fuel such as city gas, LPG and other petroleum-based fractions, and concentrates the liquid mainly using a burner 26, a combustion gas injection pipe 27, and a submerged combustion type concentrator 25. Is performed.

Numeral 8 denotes, for example, an aqueous solution of LiBr having a concentration of about 53%, which is supplied to 25 after being heated by the high-temperature concentrated liquid 7 while passing through the liquid-liquid heat exchanger 32 by the recovery pump 31. The fuel 28 and the combustion air 29 are sent to 26, and the high-temperature gas obtained by the complete combustion is jetted into the liquid retained at 25 through 27.

Very good heat exchange takes place between the high-temperature gas dispersed as fine bubbles in the liquid and the liquid, and the water vapor evaporated by the heating of the liquid is separated from the liquid surface by the combustion gas and exhausted. Get out of the system as 30.

At this time, the concentration of the can solution is adjusted to, for example, about 63% of LiBr, and is taken out as a concentrated regenerating solution by the solution sending pump 33.
Give heat to 8 while passing through 32-cool yourself. This is further reduced to a predetermined temperature, for example, 40
After cooling to around ℃, return to the top of 3 as 7.

This concentration operation is performed under normal pressure in the can itself, but 29 requires a pressure loss corresponding to the pressure loss inside the burner and the tip of 27 is set slightly below the liquid surface.

The above is an example in which a high-temperature gas obtained by completely burning a fluid fuel together with air as a heat source is brought into direct contact with a diluted absorption liquid to concentrate and regenerate the same, but other high-temperature exhaust gas (eg, engine exhaust) or the like is used. A similar operation can be performed. As a method of direct contact between the high-temperature gas and the liquid, in addition to jetting the gas into the liquid, known methods such as a method of contacting gas and liquid on the surface of a filler such as ceramics and a method of spraying a liquid into a hot gas are known. The method can be appropriately applied.

A known method of concentrating the absorbing solution under reduced pressure using steam or hot water as in the case of the absorption refrigerator can also be employed if the unit price of the calorific value is low.

[Example] The air conditioning during the daytime in summer is planned according to the flow sheet of FIG. In this case, the air precooler 9 is omitted. Table 1 shows the conditions of the temperature and humidity of the indoor air, the outdoor air, and the return air 18 at this time. Each symbol A, B, C ... is the second
Corresponding to positions A, B, C,... On the psychrometric chart shown in the figure. At this time, the mixing ratio of indoor air and outdoor air was 0.80 / 0.20
The incoming air 1 is defined as (on a dry air basis).

Next, the liquid temperature at each point on the flow sheet and LiBr
The concentration of the absorbing solution is determined as shown in Table 2.

At this time, the temperature and humidity at each point of this system can be set as shown in Table 3 by appropriately selecting the models 10 and 12, the heat transfer area, and the air linear velocity.
It is possible to set a plan as follows.

At this time, the ratio of the return air 19 to the return air 18 is 19.6 / 80.4
Is calculated, and the amount corresponding to the air taken in from outside for ventilation is rejected as exhaust air.

Starting with the setting of the receiving air as described above, its dehumidification, cooling, adjustment of the return air by evaporation of adiabatic water, behavior of the return air, etc. are all shown in FIG. 2, A, B, C, D, E, F, It is indicated by each point of G and H.

In this system, the selection of the temperature difference between the heat exchangers 5 and 12 is important in terms of equipment costs.

 Table 4 shows the temperature difference under the above conditions.

Although these are all low temperature differences, they are in the practical range. Also, make-up water is about 0.7% by weight of the received air quantity 1 to be treated in combination with 15, 23, and the evaporation loss when the cooling water 6 is regenerated in the cooling water tower is expected to be about 0.5%. This is a comparable and not particularly problematic consumption compared to conventional mechanical or absorption refrigeration systems.

Next, referring to FIG. 1, the operating conditions for obtaining the concentrated absorbing solution 7 by performing the concentration regeneration of the diluted LiBr solution 8 discharged from 3 and the expected results will be described.

City gas is used as fuel. Table 5 shows the composition and the calorific value.

Table 5 Fuel Specifications composition methane (CH ₄₎ of (city gas) to about 82% ethane (C ₂ H ₆₎ about 6% propane (C ₃ H ₈₎ 4% butane (C ₄ H ₁₈₎ about 2% high A calorific value of about 10,800 kcal / Nm ^{3 Using} this fuel, a combination of a burner 26, a submerged combustion type concentrator 25, a liquid-liquid heat exchanger 32 and a liquid cooler 34 using cooling water 35 as shown in FIG. To perform the concentration regeneration of the absorbing solution. Table 6 shows the operating conditions and expected values obtained.

Table 6 Operating conditions for concentration and regeneration of absorbents Fuel City gas (see Table 5) Air rate 1.25 Absorbent Temperature and concentration as shown in Table 2.

Tank temperature 141 ° C Exhaust gas 30 141 ° C, Humidity 0.706 [kg / kg] Heat loss 8% against high input combustion heat Condensed heat efficiency 61.1% (vs input high combustion heat) The exhaust gas has a dew point of 83 ° C and wet bulb temperature The enthalpy of keeping 84 ° C and taking it out of the system is equivalent to about 10% of the heat input.
If necessary, by using a heat exchanger or performing direct heat exchange by contacting with water, hot water of 60 ° C. or more can be easily recovered from the exhaust gas.

Combining the above, the incoming air 1 is treated 1000 kg and returned air
About 800 kg of 18 can be obtained, but the required cooling amount is 751
For 5 kcal (2.26 refrigeration tons), the required fuel consumption is 6.80 kcal (higher heat generation standard), which is a COP conversion value of 1.10.

Of course, if the hot water is recovered and used as described above, the thermal efficiency is further increased.

[Effects of the Invention] The present invention is configured as described above and has the following effects. First, according to the present invention, in order to make indoor environmental conditions comfortable in summer, the temperature and the humidity can be separately determined and the operation corresponding thereto can be performed. This is also possible when the system is operated for winter heating, as described below.

The second effect is that it utilizes the property that the water vapor partial pressure of LiBr solution or the like changes depending on its concentration and temperature, and uses a heat source for its regeneration. In this respect, it is the same as a known absorption refrigerator. Therefore, power consumption is only required for driving auxiliary equipment such as a pump and a blower.

As the heat source, city gas, combustion gas of various petroleum fractions, and medium-high temperature exhaust gas can be used. In this case, it is not necessary to use steam or hot water, particularly by using a boiler or the like, and it is possible to directly contact the absorbing solution under normal pressure to perform the concentration regeneration.

For this reason, highly economical operation can be performed with high thermal efficiency using inexpensive energy. Third, while the known absorption refrigerator is operated under vacuum and many heat exchanger groups need to be incorporated in the system, the present invention is operated under normal pressure and the number of heat exchangers is also small. Less than half. In addition, each element is simple and small, and can be designed and manufactured by a standard method using inexpensive materials, except for some parts.

Therefore, equipment costs are low and maintenance and inspection are easy. 4th
Is the versatility of this system. Although the above description is for cooling in summer, it can be used for heating in winter simply by changing the operating conditions of this system, so that the equipment can also be used for cooling and heating.

 This will be described with reference to the system shown in FIG.

For example, when the outside air condition in winter is 0 ° C and humidity is 0.0017 [kg / k
g], and the indoor air condition shall be maintained at 20 ° C and humidity of 0.0073 [kg / kg] while taking this in for ventilation. On the other hand, while the incoming air 1 passes through 3, the liquor, ie, the latent heat, is supplied from the working fluid of LiBr together with the sensible heat, and the exhaust from the top of the tower reaches 30 ° C. and the humidity reaches 0.0073 [kg / kg]. It can be set so that it is blown into the room as return air.

For that purpose, 25 may be operated so as to maintain the LiBr liquid returning to the top of column 3 at 50%, around 35 ° C. At this time, the purpose of 25 is simply to raise the temperature of the liquid by heating, and the water is replenished in the can liquid with the amount lost in 3 for the humidification of the air, contrary to the summer. In this case, a heat exchanger, a cooler, a cooling water tower and its peripheral devices are not required.

In the description so far, as a means for dehumidifying and drying the received air 1, it has been described that water is absorbed solely by contact with an aqueous solution of LiBr, but the present invention is not limited to this. For example, a known aqueous solution of triethylene glycol (C ₆ H ₁₄ O ₄ ) or the like may be used for dehumidifying a gas depending on conditions. Also, a method of impregnating a porous filler with a mixture of a known crystal of LiBr or the like and a saturated liquid thereof and contacting the surface with air to absorb the moisture or silica gel,
Naturally, it is also possible to use an adsorbent such as molecular sieve as a means for dehumidifying and drying air.

[Brief description of the drawings]

FIG. 1 is a flow sheet showing an example of an air conditioning method using latent heat of vaporization of water. FIG. 2 is a psychrometric chart showing the values of the temperature and humidity of air corresponding to each point on the flow sheet of the embodiment. The horizontal axis is the air temperature, and the vertical axis is the humidity [kg moisture / kg dry air]. ]. DESCRIPTION OF SYMBOLS 1 ... Intake air, 2 ... Blower 3 ... Air dehumidification tower, 4 ... Packing layer 5 ... Cooling pipe, 6 ... Cooling water 7 ... Rich absorption liquid, 8 ... Dilution absorption liquid 9 ... Air precooler, 10 ... Cooling pipe 11 ... Cooling water, 12 ... Air heat exchanger 12h ... Heat exchange high temperature section, 12C ... Heat exchange low temperature section 13 ... Heat transfer mechanism, 14 ... Adiabatic water evaporator 15 ... Injection, 16 ... Spray nozzle 17 ... Air distribution Valve, 18 ... Return air 19 ... Reflux air, 20 ... Water injection nozzle 21 ... Separation tank, 22 ... Circulation pump 23 ... Make-up water, 24 ... Discharge air 25 ... Submerged combustion type concentrator, 26 ... Burner 27 ... Combustion gas ejection Pipe, 28 ... Fuel 29 ... Combustion air, 30 ... Exhaust gas 31 ... Recovery pump, 32 ... Liquid heat exchanger 33 ... Liquid sending pump, 34 ... Liquid cooler 35 ... Cooling water A ... Indoor air, B ... Outdoor air C: Incoming air 1, D: Return air 18 E: Dry air (12h inlet), F: Dry air (12h outlet) G: Reflux air 19 (12c inlet) H ... Discharge air 24 (12c outlet)

Claims (1)

(57) [Claims] After dehumidifying incoming air by an air dehumidifier, the air is introduced into a high-temperature side of a heat exchanger and cooled, and the cooled air is brought into contact with a predetermined amount of water to provide adiabatic water. Cooling and humidification by evaporation of water to obtain return air,
When exchanging heat through the heat transfer mechanism 13 with the high-temperature air flowing back to the low-temperature side 12c and flowing through the 12h through the heat-transfer mechanism 13, the air is constantly brought into contact with water to keep the temperature close to the wet-bulb temperature and exhaust air. An air conditioning method using latent heat of evaporation of water.