CN113803799B - Combined type terminal device, air conditioning unit and dehumidification compensation adjustment method thereof - Google Patents

Abstract

The present invention discloses a combined terminal device, an air conditioning unit using the combined terminal device, and a dehumidification compensation adjustment method thereof. The combined terminal device comprises an integrated medium-temperature heat exchanger and a low-temperature heat exchanger. The supply and return water pipes of the medium-temperature heat exchanger are connected to the medium-temperature chiller for cooling the indoor return air; the supply and return water pipes of the low-temperature heat exchanger are connected to the low-temperature chiller for supercooling and dehumidifying the air after the cooling and cooling treatment. The present invention solves the problem of decreased dehumidification capacity of the terminal fan coil caused by increasing the chilled water supply temperature and reduces the increased energy consumption caused by reducing the chilled water supply temperature.

Description

Combined terminal device, air conditioning unit and dehumidification compensation adjustment method thereof

Technical Field

The present invention relates to the technical field of air conditioning, and in particular to a combined terminal device, an air conditioning unit using the combined terminal device, and a dehumidification compensation adjustment method thereof.

Background Art

In recent years, as the temperature of chilled water increases, the efficiency of the main engine of the medium-temperature water system has been significantly improved and has been widely studied and applied. Taking the commonly used 11℃ inlet water as an example, if the main engine outlet water temperature increases by 4℃, the evaporation temperature increases by 3.5℃, and the main engine energy efficiency increases by about 12%.

Conventional air conditioning terminal fan coil units are rated for cooling under standard operating conditions (inlet air dry bulb temperature 27°C, wet bulb temperature 19.5°C) with a water inlet temperature of 7°C, a water outlet temperature of 12°C, and a supply and return water temperature difference of 5°C. When the inlet water temperature is above 9°C and the return water temperature increases, the water supply needs to be increased to meet the load required by the engineering design, which will increase the energy consumption of the chilled water circulation pump. In addition, for every 1°C increase in the inlet water temperature of conventional fan coil units, the performance decreases by about 12% and the dehumidification capacity decreases by 30%. Dehumidification is generally increased by increasing the air volume, but for conventional fan coil units, when the inlet water temperature is above 9°C, it is difficult to meet the indoor comfort requirements by simply increasing the air volume, and there is almost no obvious dehumidification function.

It can be seen that how to increase the chilled water supply temperature without reducing the dehumidification capacity of the terminal fan coil unit and solve the dehumidification capacity of the terminal device has become the core issue of the medium-temperature water system.

Summary of the invention

The present invention proposes a combined terminal device, an air-conditioning unit and a dehumidification compensation adjustment method thereof to solve the problems existing in the prior art of decreasing the dehumidification capacity of the terminal fan coil unit due to increasing the chilled water supply temperature and reducing the increased energy consumption due to reducing the chilled water supply temperature.

The present invention proposes a combined terminal device, including a medium-temperature heat exchanger and a low-temperature heat exchanger of integrated design. The supply and return water pipes of the medium-temperature heat exchanger are connected to the medium-temperature chiller for cooling the indoor return air; the supply and return water pipes of the low-temperature heat exchanger are connected to the low-temperature chiller for supercooling and dehumidifying the air after cooling.

Preferably, a first water flow regulating valve is provided on the water inlet pipe of the medium-temperature heat exchanger, and a second water flow regulating valve is provided on the water inlet pipe of the low-temperature heat exchanger.

Preferably, the medium-temperature heat exchanger and the low-temperature heat exchanger are both fin-tube heat exchangers, and are fixedly connected into one body through side connecting plates and connecting devices.

Preferably, both the medium-temperature heat exchanger and the low-temperature heat exchanger use internally threaded pipes, and the fin spacing of the medium-temperature heat exchanger is greater than the fin spacing of the low-temperature heat exchanger.

The pipe diameter of the medium-temperature heat exchanger is larger than the pipe diameter of the low-temperature heat exchanger, or is the same as the pipe diameter of the low-temperature heat exchanger.

In the first embodiment, the medium-temperature heat exchanger includes three rows of pipes, and the low-temperature heat exchanger includes one row of pipes. The pipe diameters of the medium-temperature heat exchanger and the low-temperature heat exchanger are both Φ7 mm.

In the second embodiment, the medium-temperature heat exchanger includes three rows of pipes, the low-temperature heat exchanger includes one row of pipes, the pipe diameter of the medium-temperature heat exchanger is Φ7 mm, and the pipe diameter of the low-temperature heat exchanger is Φ5 mm.

In the third embodiment, the medium-temperature heat exchanger includes two rows of pipes, and the low-temperature heat exchanger includes two rows of pipes. The pipe diameter of the medium-temperature heat exchanger is Φ7 mm, and the pipe diameter of the low-temperature heat exchanger is Φ5 mm.

The present invention further provides an air conditioning unit, comprising a medium-temperature chiller and a low-temperature chiller, wherein the terminal device of the air conditioning unit adopts the above-mentioned combined terminal device.

The present invention also proposes a dehumidification compensation adjustment method for the above-mentioned air-conditioning unit, wherein the controller of the air-conditioning unit controls the operation mode of the air-conditioning unit according to the cold air ratio and the supply air temperature difference output by the combined terminal device.

The dehumidification compensation adjustment method comprises:

Step 1. Turn on the medium-temperature chiller and the medium-temperature water flow regulating valve;

Step 2. Calculate the actual air volume G and cooling capacity Qa of the medium temperature chiller, and the cooling air ratio and supply air temperature difference of the output combined terminal device;

Step 3. Select the operation mode of the air conditioning unit according to the range of the cooling air ratio and the supply air temperature difference.

The operating modes include:

Mode 1: When the cooling air ratio is ≥A and the supply air temperature difference is >C, the unit is overcooled, and the speed of the fan in the terminal combined heat exchanger is reduced to reduce the air volume;

Mode 2: When the cooling air ratio is ≥A and the supply air temperature difference is between B and C degrees, the cooling and dehumidification are normal, and the current operating state of the air conditioning unit is maintained;

Mode 3: When the cooling air ratio is less than A and the supply air temperature difference is between B and C degrees, the dehumidification capacity is small, and the speed of the fan in the combined terminal device is increased to increase the air volume;

Mode 4: When the cold air ratio is less than A and the supply air temperature difference is less than B degrees, there is no dehumidification capacity, and the low-temperature chiller and the low-temperature water regulating valve are turned on.

Preferably, the A value is 4, the B value is 11 degrees, and the C value is 16 degrees.

The mode four also includes: calculating the water-side heat exchange rate _Qwater and the air-side heat exchange rate _Qair of the low-temperature heat exchanger, and comparing the difference between the water-side heat exchange rate _Qwater and the air-side heat exchange rate _Qwater and the ratio of the water-side heat exchange rate _Qwater . When the ratio is less than or equal to D, the cold air ratio and the supply air temperature difference are calculated according to the total cooling capacity Q and the outlet air temperature tb2 of the combined terminal device, and returning to step 3; when the ratio is greater than D, the opening of the low-temperature water volume regulating valve is increased.

Preferably, the D value is 5%.

Compared with the prior art, the present invention has the following beneficial effects:

1. The present invention fully utilizes the structural space of the existing fan coil unit by designing a combined structure of a medium-temperature water heat exchanger and a low-temperature water heat exchanger, and solves the technical problems of low performance, poor dehumidification effect and poor indoor comfort of the medium-temperature water fan coil unit system;

2. The present invention improves the heat exchange efficiency of the heat exchanger under medium-temperature water conditions and enhances the latent heat performance of the heat exchanger through a set of precise adjustment methods for enhancing the dehumidification of the heat exchanger. At the same time, the dehumidification capacity of the heat exchanger is enhanced by the low-temperature heat exchanger, thereby solving the problems of poor indoor comfort of the medium-temperature water fan coil air-conditioning system and high energy consumption of a single low-temperature water fan coil. It provides a comprehensive solution for the development and design of terminal products of the medium-temperature water system, and plays a positive role in achieving the national carbon peak and carbon neutrality goals for building energy conservation.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is described in detail below with reference to the accompanying drawings and specific embodiments, wherein:

FIG1 is a schematic diagram of the three-dimensional structure of the combined terminal device proposed by the present invention;

FIG2a is a schematic diagram of a first embodiment of a combined terminal device provided by the present invention;

FIG2 b is a schematic diagram of a second embodiment of the combined terminal device proposed by the present invention;

FIG2c is a schematic diagram of a third embodiment of the combined terminal device provided by the present invention;

FIG3 is a graph showing the outlet air temperature of the combined terminal device proposed by the present invention;

FIG4 is a system schematic diagram of the air conditioning unit proposed by the present invention;

FIG5 is a flow chart of dehumidification control of the combined terminal device of the present invention.

DETAILED DESCRIPTION

In order to make the purpose, technical solution and advantages of the present invention clearer, the present invention is described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the following specific embodiments are only used to explain the present invention and do not constitute a limitation to the present invention.

As shown in Figures 1 and 4, the combined terminal device 1 proposed in the present invention includes a medium-temperature heat exchanger 2 and a low-temperature heat exchanger 3. The water supply and return pipes of the medium-temperature heat exchanger are connected to the medium-temperature chiller 5 for cooling the indoor return air. The water supply and return pipes of the low-temperature heat exchanger are connected to the low-temperature chiller 6 for supercooling and dehumidifying the air after cooling. A first water flow regulating valve 4 is provided on the water inlet pipe of the low-temperature heat exchanger, and a second water flow regulating valve is provided on the water inlet pipe of the medium-temperature heat exchanger. The second water flow regulating valve is arranged on the other side and is not shown in the figure. The medium-temperature heat exchanger 2 and the low-temperature heat exchanger 3 are spliced and combined into one by side connecting plates and connecting devices. In this embodiment, the connecting device is connected by screws.

The medium-temperature heat exchanger 2 is close to the return air side and is mainly a cooling function section. The low-temperature heat exchanger 3 is connected to the medium-temperature heat exchanger and is mainly a dehumidification function section. The medium-temperature heat exchanger adopts a high-efficiency internally threaded tube with a large diameter and a large fin pitch structure. The main purpose is to enhance the sensible heat transfer dominated by the temperature difference. At the same time, the large fin pitch reduces the wind resistance and increases the oncoming wind speed to improve the heat transfer coefficient for the next dehumidification function section. The low-temperature heat exchanger adopts a high-efficiency internally threaded tube with the same or different diameters and a small fin pitch structure. The main purpose is to enhance the latent heat transfer dominated by the enthalpy difference. At the same time, reducing the fin pitch can increase the number of fins, enhance the condensation of condensed water on the fin surface, and improve the dehumidification effect.

In the first embodiment, the medium-temperature heat exchanger 2 includes three rows of pipes, and the low-temperature heat exchanger 3 includes one row of pipes. The pipe diameters of the medium-temperature heat exchanger and the low-temperature heat exchanger are both Φ7 mm, as shown in FIG. 2a.

In the second embodiment, the medium temperature heat exchanger 2 includes three rows of pipes, and the low temperature heat exchanger 3 includes one row of pipes. The pipe diameter of the medium temperature heat exchanger is Φ7 mm, and the pipe diameter of the low temperature heat exchanger is Φ5 mm, as shown in FIG. 2b .

In the third embodiment, the medium temperature heat exchanger 2 includes two rows of pipes, and the low temperature heat exchanger 3 also includes two rows of pipes. The pipe diameter of the medium temperature heat exchanger is Φ7 mm, and the pipe diameter of the low temperature heat exchanger is Φ5 mm, as shown in FIG. 2c.

The working principle of the combined terminal device: along the air flow direction (from the return air side to the outlet air side of the fan coil unit), the air absorbs cold and the temperature decreases, that is, the air temperature gradually decreases from the first row of heat exchange tubes to the last row of heat exchange tubes of the medium-temperature heat exchanger, so that the high-temperature indoor return air is first cooled with a large temperature difference, and then the air continues to flow to the first row of heat exchange tubes to the last row of heat exchange tubes of the low-temperature heat exchanger, and the supercooling and dehumidification treatment with large flow rate and small temperature difference to enhance heat exchange is carried out, finally realizing the refrigeration and dehumidification function of the enhanced terminal device and greatly improving the heat exchange efficiency.

Figure 3 is a curve of the outlet air temperature of the fan coil unit using a combined terminal device. From Figure 3, we can see the comparison results of the measured data: when the inlet water temperature of the conventional fan coil unit is 11°C and the outlet water temperature is 16°C, the outlet air temperature is 15.8°C, and there is no dehumidification effect; when the inlet water temperature of the combined fan coil unit medium-temperature heat exchanger is 11°C and the outlet water temperature is 16°C, and the inlet water temperature of the low-temperature heat exchanger changes from 7-10°C, the outlet air temperature is lower than 15.8°C, which effectively strengthens the heat exchange and increases the dehumidification effect.

The experimental results show that when the low-temperature heat exchanger has 7℃ inlet water and a 5℃ temperature difference, the dehumidification capacity increases by about 98.8%;

When the low-temperature heat exchanger has an inlet water temperature of 8°C and a temperature difference of 5°C, the dehumidification capacity increases by about 60%; when the low-temperature heat exchanger has an inlet water temperature of 9°C and a temperature difference of 5°C, the dehumidification capacity increases by about 15%.

FIG4 is a system schematic diagram of the air conditioning unit proposed by the present invention. The air conditioning unit includes a medium-temperature chiller 5 and a low-temperature chiller 6, wherein the terminal fan coil adopts the combined structure proposed by the present invention. The chilled water discharged from the medium-temperature chiller 5 is sent to the medium-temperature heat exchanger 2 through the water distributor 7 and the second water volume regulating valve, and after heat exchange with the indoor return air, it returns to the medium-temperature chiller through the water collector 8 to exchange heat with the evaporator and then recirculates. The chilled water discharged from the low-temperature chiller 6 is sent to the low-temperature heat exchanger 3 through the water distributor 7 and the first water volume regulating valve 4, and heat exchanged with the air cooled by the medium-temperature heat exchanger, and then returned to the low-temperature chiller through the water collector 8 to exchange heat with the evaporator and then recirculate. The cooling water of the medium-temperature chiller 5 and the low-temperature chiller 6 is sent to the cooling tower 9 for cooling after heat exchange with the condenser and then recycled.

The dehumidification compensation adjustment method for an air conditioning unit proposed by the present invention comprises:

Step 1. Turn on the medium-temperature chiller and the medium-temperature water flow regulating valve;

Step 2. Calculate the actual air volume G of the medium-temperature chiller, the cooling capacity Qa of the medium-temperature heat exchanger, and the cold air ratio and supply air temperature difference of the output combined terminal device;

Step 3. Select the operation mode of the air conditioning unit according to the range of the cooling air ratio and the supply air temperature difference.

The following uses the FP-102WAS/G model as an example and combines Figure 5 to explain the principle of enhanced dehumidification control for medium and low temperature combined fan coil units:

(1) Start the medium-temperature heat exchanger 2 when starting up, input the whole machine model, return air dry bulb temperature t1, return air wet bulb temperature ts1, outlet air dry bulb temperature t2, outlet air wet bulb temperature ts2, medium-temperature water inlet temperature tw1;

(2) The controller of the unit calculates the actual circulating air volume G, the cooling capacity Qa of the medium-temperature heat exchanger, the output cooling air ratio, and the supply air temperature difference;

(3) Pattern recognition judgment:

a. When the cooling air ratio is ≥4 and the supply air temperature difference is >16℃, it is identified as mode 1, the unit is overcooled, and the fan speed is lowered to reduce the return air volume: the air volume lowered each time is the set value, and after adjustment, return to step 2 until it is adjusted to meet the indoor comfort requirements;

b. When the cooling air ratio is ≥ 4 and the air supply temperature difference is between 11-16°C, it is identified as mode 2, normal cooling and dehumidification, no adjustment of the fan speed, normal operation, and return to step 2;

c. When the cold air ratio is less than 4 and the supply air temperature difference is between 11-16℃, it is identified as mode 3, the dehumidification capacity is small, and the air volume is increased. The increased air volume each time is the set value. After adjustment, return to step 2 until the indoor comfort requirements are met;

d. When the cold air ratio is less than 4 and the supply air temperature difference is less than 11°C, it is identified as mode 4. At this time, the unit has no dehumidification capacity and needs to start the low-temperature chiller, open the first water volume regulating valve, and start the low-temperature heat exchanger. At this time, the unit controller accurately calculates the performance of the low-temperature heat exchanger, outputs the cooling capacity of the medium-temperature heat exchanger Qb, the cooling capacity of the low-temperature heat exchanger Qb, the cooling capacity of the low-temperature heat exchanger Qb, the total cooling capacity of the unit Q=Qa+Qb, the circulating air volume G, the outlet air temperature tb2, and calculates the cold air ratio and the supply air temperature difference, and then returns to step 3 until it is adjusted to meet the indoor comfort range.

The calculation of the cooling air ratio of the fan coil unit is as follows:

Circulation air volume G Inlet dry bulb temperature t1 Inlet wet bulb temperature ts1 Inlet air humidity d1 Air outlet dry bulb temperature t2 Wet bulb temperature ts2 Inlet air specific enthalpy h1 Air Density e Heat exchanger contact coefficient E1 Outlet air specific enthalpy h2 Cooling ratio Y Specific heat of air Cpa

Inlet air enthalpy: h1=1.006* t1+ d1*(2501+1.805*t1);

Specific heat capacity: Cpa=1.005+1.805*d1;

Sensible cooling capacity per unit mass of air: qs = Cpa*(t1-t2);

Total cooling capacity per unit mass of air: q = h1- h2;

Sensible heat ratio = qs/ q = Cpa*( t1- t2)/(h1- h2);

The heat exchanger contact coefficient is obtained from actual measurements of the unit, and the conventional fan disc E1=0.88;

Wet bulb temperature at outlet: ts2 = t2-(1- E1)*(t1- ts1);

The humidity content of the outlet air d2 can be found in the humidity chart by the two parameters t2 and ts2;

Outlet air enthalpy: h2=1.006*t2+d2*(2501+1.805*t2);

Cold air ratio Y = total cooling capacity/circulating air volume = G*q*e/g*3.6 = (h1- h2)*e/3.6 = f(t2).

Therefore, the cooling air ratio is only a composite function of the outlet dry-bulb temperature. The accurate cooling air ratio Y can be obtained by accurately calculating t2.

The dehumidification compensation adjustment method for air-conditioning units proposed in the present invention is a precise control method by enhancing the dehumidification of the heat exchanger. It can not only improve the heat exchange efficiency of the heat exchanger under medium-temperature water conditions and enhance the latent heat performance of the heat exchanger, but also solve the problem of high energy consumption under low-temperature water conditions by enhancing the capacity of the heat exchanger. It meets the indoor comfort requirements, provides a comprehensive solution for the development and design of terminal products of medium-temperature water systems, and plays a positive role in achieving the national carbon peak and carbon neutrality goals for building energy conservation.

The above description is only a specific implementation of the present invention. It should be pointed out that any modification, equivalent substitution and change made within the spirit and framework of the present invention should be included in the protection scope of the present invention.

Claims (13)

1. The dehumidification compensation regulation method of the air conditioning unit comprises a medium temperature water chilling unit and a low temperature water chilling unit, and is characterized by further comprising a combined end device formed by a medium temperature heat exchanger and a low temperature heat exchanger, wherein a water supply and return pipeline of the medium temperature heat exchanger is communicated with the medium temperature water chilling unit, a water supply and return pipeline of the low temperature heat exchanger is communicated with the low temperature water chilling unit,

The controller of the air conditioning unit controls the operation mode of the air conditioning unit according to the cold air ratio and the air supply temperature difference output by the combined type tail end device, and the controller comprises:

Step 1, starting a medium-temperature water chilling unit and a medium-temperature water quantity regulating valve;

Step 2, calculating the cold air ratio and the air supply temperature difference of the combined type tail end device;

Step 3, selecting an operation mode of the air conditioning unit according to the range of the cold air ratio and the air supply temperature difference;

the operation modes include:

in the first mode, when the cold air ratio is more than or equal to A and the air supply temperature difference is more than C degrees, the unit is supercooled, the rotating speed of a fan in the tail end combined heat exchanger is reduced, and the air quantity is reduced;

mode two, when the cold air ratio is more than or equal to A and the air supply temperature difference is between B and C degrees, the temperature reduction and dehumidification are normal, and the current running state of the air conditioning unit is maintained;

mode three, when the cold air ratio is less than A and the air supply temperature difference is between B and C degrees, the dehumidifying capacity is smaller, the rotating speed of a fan in the combined type tail end device is increased, and the air quantity is improved;

And in the fourth mode, when the cold air ratio is less than A and the air supply temperature difference is less than B ℃, the dehumidification capacity is not achieved, and the low-temperature water chilling unit and the low-temperature water quantity regulating valve are opened.

2. The dehumidification compensation adjustment method of claim 1, wherein the a value is 4, the B value is 11 degrees, and the C value is 16 degrees.

3. The dehumidification compensation adjustment method according to claim 1, wherein the fourth mode further comprises: calculating the water side heat exchange quantity Q _{Water and its preparation method} and the air side heat exchange quantity Q _{Empty space} of the low-temperature heat exchanger, comparing the ratio of the difference value of the water side heat exchange quantity Q _{Water and its preparation method} and the air side heat exchange quantity Q _{Water and its preparation method} to the water side heat exchange quantity Q _{Water and its preparation method} , calculating the cold air ratio and the air supply temperature difference according to the total cold quantity Q and the air outlet temperature tb2 of the combined type tail end device when the ratio is smaller than or equal to D, and returning to the step 3; when the ratio is greater than D%, the opening degree of the low-temperature water amount regulating valve is increased.

4. A dehumidification compensation adjustment method according to claim 3, wherein the D value is 5%.

5. An air conditioning unit comprising a medium temperature water chiller and a low temperature water chiller, and further comprising a combined end device assembled by a medium temperature heat exchanger and a low temperature heat exchanger, wherein the controller of the air conditioning unit performs dehumidification compensation adjustment on the air conditioning unit by adopting the dehumidification compensation adjustment method according to any one of claims 1-4.

6. The air conditioning unit as set forth in claim 5, wherein the water supply pipeline of the medium temperature heat exchanger is communicated with the medium temperature water chilling unit for cooling the indoor return air; and a water supply pipeline of the low-temperature heat exchanger is communicated with the low-temperature water chilling unit and is used for supercooling and dehumidifying the air after cooling treatment.

7. The air conditioning unit according to claim 5, wherein a first water quantity regulating valve is provided on a water inlet pipe of the low temperature heat exchanger, and a second water quantity regulating valve is provided on a water inlet pipe of the medium temperature heat exchanger.

8. The air conditioning unit as set forth in claim 5, wherein said medium temperature heat exchanger and said low temperature heat exchanger are fin tube heat exchangers and are fixedly joined together by side connection plates and connection means.

9. The air conditioning unit as set forth in claim 5, wherein said medium temperature heat exchanger and said low temperature heat exchanger each employ an internally threaded tube, and wherein the fin pitch of said medium temperature heat exchanger is greater than the fin pitch of said low temperature heat exchanger.

10. The air conditioning unit of claim 5, wherein the tube diameter of the medium temperature heat exchanger is greater than or the same as the tube diameter of the low temperature heat exchanger.

11. The air conditioning unit as set forth in claim 10, wherein said medium temperature heat exchanger comprises three rows of tubes, said low temperature heat exchanger comprises a row of tubes, and the tube diameters of said medium temperature heat exchanger and said low temperature heat exchanger are each Φ7 mm.

12. The air conditioning unit according to claim 10, wherein the intermediate temperature heat exchanger comprises three rows of pipes, the low temperature heat exchanger comprises one row of pipes, the pipe diameter of the intermediate temperature heat exchanger is Φ7 mm, and the pipe diameter of the low temperature heat exchanger is Φ5 mm.

13. The air conditioning unit according to claim 10, wherein the intermediate temperature heat exchanger comprises two rows of pipes, the low temperature heat exchanger comprises two rows of pipes, the pipe diameter of the intermediate temperature heat exchanger is Φ7 mm, and the pipe diameter of the low temperature heat exchanger is Φ5 mm.