WO2011087163A1

WO2011087163A1 - Variable air volume system

Info

Publication number: WO2011087163A1
Application number: PCT/KR2010/000196
Authority: WO
Inventors: Jin Soo Oh; Jun Ho Cho; Jung Kyu Yang; Jae Sin Choi
Original assignee: Carrier Corporation
Priority date: 2010-01-12
Filing date: 2010-01-12
Publication date: 2011-07-21
Also published as: EP2524174A1

Abstract

The present disclosure relates to a variable air volume ("VAV") system. A method of controlling a fan of a variable air volume system, includes determining a degree of openness of at least one damper based on temperature data of at least one zone, determining weights for the degree of openness of the at least one damper, multiplying the degree of openness with the weights to produce a weighted degree of openness of the at least one damper, summing the weighted degree of openness of the at least one damper to obtain a summation result of the weighted degree of openness, and controlling a revolution speed of the fan based on the summation result.

Description

VARIABLE AIR VOLUME SYSTEM

The present disclosure relates to a variable air volume ("VAV") system, in particular, to control the operation of a fan in a VAV system.

Conventionally, VAV systems have had a pressure sensor installed in a duct, through which air flow is supplied to a respective zone to be served so that a fan could be controlled in accordance with the volume of air flow monitored by the pressure sensors. For example, the pressure sensor sends a signal indicative of the volume of air flow for use of controlling the fan's speed. In this case, a plurality of pressure sensors need to be carefully installed in a proper place so that the pressure signals, which the sensors sense, closely represent the actual air flow of the system. In addition to the pressure sensors, temperature sensors may be also used to control the fan in the VAV systems. Temperature sensors may be located in the zones air flow is provided and may provide data regarding how much of a cooling or heating load is required in each zone. The VAV system may use the cooling or heating data to control the fan speed.

However, conventional VAV systems have been found to be unsatisfactory in providing energy efficient, comfortable, and stable cooling to each of the zones to be served, even when the systems use a plurality of expensive pressure and temperature sensors. Accordingly, the combination of pressure and temperature sensors may not be suitable for controlling a fan in a VAV system, and therefore it may be necessary to control the fan of the VAV system effectively and efficiently using different measurements.

The present disclosure is directed to controlling a fan in a VAV system taking into account that heating sources exist in each zone to be served and that there is a loss in conditioned air flow during delivery to each zone.

The method of controlling a fan of a VAV System, according to the present disclosure includes determining a degree of openness for at least one damper based on temperature data of at least one zone; determining a weight for the degree of openness of the at least one damper; using the degree of openness with the weight to ascertain a weighted degree of openness of the at least one damper ; using the weighted degree of openness of the at least one damper to obtain a reference value for revolution speed of a fan; and controlling the revolution speed of the fan based on the reference value.

The VAV system according to the present disclosure includes at least one damper positioned to control air to at least one zone via at least one duct; an air conditioning portion that conditions air in the at least one duct; a fan that controls the air flow in the duct; and a system controller that determines a degree of openness of the at least one damper based on temperature data of the at least one zone, determines a weight for the degree of openness of the at least one damper, uses the degree of openness with the weights to ascertain a weighted degree of openness of the at least one damper, uses the weighted degree of openness of the at least one damper to obtain a reference value for revolution speed of a fan, and controls the revolution speed of the fan based on the reference value.

Fig. 1 is an illustration of a VAV system in a building according to one embodiment of the present disclosure.

Fig. 2 is a detailed block diagram of a VAV system according to one embodiment of the present disclosure.

Fig. 3 is a graph illustrating the control scheme of a damper according to one embodiment of the present disclosure.

Fig. 4 is a flow diagram of a process for controlling an open degree of a damper according to one embodiment of the present disclosure.

Fig. 5 is a flow diagram of a process for controlling revolution speed of a fan according to one embodiment of the present disclosure.

Before turning to figures, which illustrate some illustrative embodiments in detail, it should be understood that the application is not limited to the details or methodology set forth in the description or illustrated in the figures. It should also be understood that the terminology is for the purpose of description only and should not be regarded as limiting.

Fig. 1 is a block diagram of a VAV system in a building 100 according to one embodiment of the present disclosure. Building 100 may vary significantly in terms of size, or type. For example, building 100 may have several floors including multiple zones to be served, each of which may be a room, a set of rooms or a part of a room. The zones may have the same dimensions or may differ. For example, the zones may be of different sizes, have a different number of windows of different sizes, number of residents, and number or type of heating sources.

Building 100 may be equipped to have

VAV systems

102a, 102b, and 102c for each floor.

VAV systems

102a, 102b, and 102c may be located either inside or outside of building 100. Each of the

VAV systems

102a, 102b, and 102c may have a plurality of ducts, each of which extends to each of the zones in the same floor as each VAV system. The plurality of ducts may include

supply air ducts

104a, 104b, and 104c and

return air ducts

106a, 106b, and 106c.

Supply air ducts

104a, 104b, and 104c may supply air flow conditioned by each of the

VAV systems

102a, 102b, and 102c to each zone on the floor. The

return air ducts

106a, 106b, and 106c may return air supplied to each zone to each of the

VAV systems

102a, 102b, and 102c. Additionally, the

VAV systems

102a, 102b, and 102c may be connected with a fresh air duct 108, which provides fresh air from outside of building 100.

The

VAV systems

102a, 102b, and 102c can in some embodiments be air cooled one or water cooled according to the heat exchanger or condenser used therein. By way of example, not limitation, in Fig. 1, the

VAV systems

102a, 102b, and 102c may be water cooled. Water may be provided from a cooling tower 110 and is used to condensate hot gaseous refrigerant. A cold water pipe 112 may deliver cold water from cooling tower 110 to the

VAV systems

102a, 102b, and 102c and a warm water pipe 114 may deliver warm water from the

VAV systems

102a, 102b, and 102c to cooling tower 110.

To supply conditioned air to each zone to be served, the

VAV systems

102a, 102b, and 102c may receive air via

return air ducts

106a, 106b and 106c, and/or fresh air duct 108 and change the condition of the received air by using an evaporator equipped in each VAV system. For example,

VAV systems

102a, 102b, and 102c may change the temperature, humidity, air composition and other characteristics of the received air.

A more detailed illustration of a VAV system, according to one embodiment of the present disclosure, is provided in Fig.2. VAV system 200 may have

supply air ducts

230a, 230b, 230c and 230d, and a return air duct 240 which are all coupled between each of zones A, B, C, and D and the VAV system 200.

Supply air ducts

230a, 230b, 230c and 230d may deliver conditioned air flow to zones A, B, C, and D, and the return air duct may return air from the zones A, B, C and D. It should be appreciated that the number of supply air ducts and zones coupled with the supply air ducts is variable. Furthermore, a fresh air duct 250 may provide VAV system 200 with fresh air from outside. VAV system 200 may also include air conditioning portion 202, a fan 204, a fan actuator 206,

dampers

208a, 208b, 208c and 208d, and

damper actuators

210a, 210b, 210c and 210d, all of which are connected with a system controller 212 via communication bus 214. System controller 212 may be in communication with other elements of VAV system 200 via communication bus 214.

Air conditioning portion 202 may include an evaporator, a condenser, a filter, a vapor provider or other devices associated with driving an air conditioning cycle. By way of example, not limitation, air conditioning portion 202 may include a brazed plate heat exchanger (BPHE) to liquefy refrigerant vapor by removal of heat. Refrigerant flow into the BPHE may be controlled by a digital scroll compressor, which makes variable capacity control possible. For this heat exchange operation, the air conditioning portion 202 may use water or air, although the present disclosure is directed to a water cooled system including a cooling tower coupled by a cold water pipe 260 and a warm water pipe 270. The cold water pipe 260 may be equipped with a water flow switch, a variable flow valve and a constant flow valve. The water flow switch may protect the air conditioning portion 202 by turning off the digital scroll compressor when the water is not supplied. The variable and constant flow valves may work together when a thermostat sends an input signal to supply to the BPHE either a constant flow of water if the digital scroll compressor is not operating, or a variable flow of water if the digital scroll compressor is operating. After the above process, the condensed refrigerant may go into an evaporator where heat exchange also occurs between the refrigerant and air, thereby resulting in conditioned air flow as desired.

Fan 204 may drive the conditioned air to zones A, B, C, and D. Fan 204 may be driven by fan actuator 206. For example, fan 204 may be coupled with fan actuator 206 through a mechanical linkage, gear assembly levers or the like to rotate the fan 204, thereby driving the conditioned air to zones A, B, C, and D. Fan actuator 206 may receive a control signal from system controller 212 via communication bus 214. In response to the control signal, fan actuator 206 may rotate fan 204 at a predetermined rate, so that system controller 212 can control the total volume of air to be delivered to zones A, B, C and D. By way of example, not limitation, fan actuator 206 may be a brushless DC ("BLDC") motor.

Dampers 208a, 208b, 208c, and 208d may be positioned at each supply duct delivering conditioned air flow to each of the zone A, B, C and D. Dampers 208a, 208b, 208c, and 208d may be opened incrementally between the full open and the full close positions. The

amount dampers

208a, 208b, 208c, and 208d are open may be controlled by each of the

damper actuators

210a, 210b, 210c, and 210d, respectively. That is,

damper actuators

210a, 210b, 210c, and 210d may control how much to open

dampers

208a, 208b, 208c, and 208d.

Damper actuators

210a, 210b, 210c, and 210d may receive a control signal from the system controller 212. In response to the control signal,

damper actuators

210a, 210b, 210c, and 210d may move

dampers

208a, 208b, 208c, and 208d to be opened a predetermined amount, respectively, so that system controller 212 can control the volume of air flow to be delivered to each of the zones A, B, C, and D. For example, the control signal may indicate to open each damper a certain percentage (Open%). The control signal in one embodiment is then transmitted to the

damper actuators

210a, 210b, 210c, and 210d in the form of current strength. In Fig. 3, in one practical embodiment, it is shown that the Open% signal can be mapped into the current strength transmitted to the damper actuator (where 0% open is closed, and 100% open is fully open). It should be appreciated that the number of dampers and the damper actuators varies in accordance with requirements for air conditioning in each build.

System controller 212 is operable to communicate with a plurality of elements in the VAV system 200 via communication bus 214. System controller 212 may transmit control signals to damper

actuators

210a, 210b, 210c, and 210d for controlling how much to open

dampers

208a, 208b, 208c and 208d, and/or to fan actuator 206 for controlling revolution speed of fan 204. A detailed explanation on the process for controlling how much to open

dampers

208a, 208b, 208c, and 208d and the process for controlling the revolution speed of fan 204 will be described with respect to Fig. 4 and 5, respectively. Furthermore, system controller 212 may be operable to communicate with thermostats (not drawn), which are equipped in the zones to be served, via communication bus 214. The thermostats may receive temperature set values by users, and may sense current temperature values with respect to the zones to be served. System controller 212 may receive signals indicative of temperature set values and current temperature values of each zone from the thermostats. By way of example, not limitation, system controller 212 may include a processing unit and a storage unit. The processing unit may be a general purpose processor, an application specific processor, a programmable processor, a circuit containing one or more processing components, a group of distributed processing components, a group of distributed computers configured for processing, etc. The processing unit is configured to execute and/or facilitate various control algorithms for controlling a fan's revolution speed and/or how much to open a damper . The processing unit may be communicably coupled with the storage unit. The storage unit (e.g., memory unit, memory device, storage device, etc.) may be one or more devices for storing data and/or computer code for controlling a fan's revolution speed and/or how much to open a damper. The storage unit may include RAM, ROM, EPROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage, etc. Any distributed and/or local memory device of the past, present, or future may be utilized with the systems and methods of this disclosure. According to one embodiment of the present disclosure, the processing unit may be programmable processors coupled with an EEPROM, which stores data and/or computer code for controlling a fan's revolution speed and/or how much a damper is to be open to be used for the purpose of allowing a user to configure stored data.

Fig. 4 is a flow diagram showing how to control how much to open a damper in a VAV system according to one embodiment of the present disclosure. The controlling process may be initiated via any number of activities (e.g., an initial user setting, a default setting, etc.) In one embodiment, the controlling process may be initiated automatically based on predetermined time intervals or performance characteristics, via input devices, via audio commands, or any combination thereof. For example, the controlling process may start with setting a temperature for each zone i, wherein the total number of the zones is n.

In one embodiment a temperature set value of zone i ("Temp_S_i") and a current temperature value of zone i ("Temp_C_i") from a thermostat installed in each of zone i is received (step 402). The difference between Temp_S_i and Temp_C_i may be calculated (step 404). The difference of zone i may be defined as Temp_Ref_a_i as follows:

MathFigure 1

Furthermore, in order to provide more stable control of how much to open a damper, the summation of a certain number of past Temp_Ref_a_i may be calculated (step 406). According to one embodiment, the summation may sum 20 latest Temp_Ref_a_i. The summation of zone i may be defined as Temp_Ref_b_i as follows:

MathFigure 2

Next, for the amount to open damper i ("VAV_o_i"), which is responsible for regulating the volume of air flow into zone i, may be calculated based on Temp_Ref_a_i and Temp_Ref_b_i (step 408). VAV_o_i may be determined as follows:

MathFigure 3

wherein, K_p represents a weight for Temp_Ref_a_i, and K_i represents a weight for Temp_Ref_b_i.

According to one embodiment, VAV_o_i may represent Open% and be stored in a storage unit for subsequent controls in the VAV system (step 410).

The steps 402-410 may be iterated until VAV_o_i is given to all of the dampers (for i=1 to n, i=i+1) in a VAV system (step 412).

Although the foregoing provides detailed descriptions on how to control how much to open the dampers used in a VAV system, the controlling may not be sufficient for convenient, efficient, and energy-saving air conditioning. This is partly because in a VAV system, not only dampers but also a fan of a VAV system can be involved in delivering conditioned air flow to zones to be served. In this regard, the present disclosure also suggests a way to control a fan's operation in a VAV system as well as the dampers as follows.

Initially, at step 502, a weight to be assigned to the openness of damper i (VAV_w_i) is determined. VAV_w_i may reflect some circumstances in each of zone i, which may include zone dimensions, windows of different sizes, number of residents, number or type of heating sources, and potential loss of conditioned air flow during delivery to zone i. For example, the VAV_w_i may be determined based on heat factors for zone i ("VAV_w_i_h_i") and loss factors for zone i ("VAV_w_i_l_i"). The heat factors for zone i ("VAV_w_i_h_i") may represent any factors which may be associated with a cooling or heating load of zone i. The VAV_w_i_h_i may include the size of the zone, the number or type of heat sources in zone i, and the number, size, type or direction of windows mounted in zone i. A heat source may be a light , a personal computer, a television, or a type of kitchen appliance existing at zone i. The loss factors for zone i ("VAV_w_i_l_i") may represent any factors which may be associated with loss of air flow during delivery to zone i. The VAV_w_i_l_i may include type, length or size of supply air ducts extending to zone i, existence or absence of a divergence in the supply air duct, and the type or number of diffusers located at the end of the supply air duct. To normalize heat factors and loss factors through all of the zones (1≤i≤n; i is an integer), the summation of VAV_w_i may be 1.

For example, VAV_w_i may be determined as follows:

Table 1

As discussed above, VAV_o_i is determined solely based on temperature data and may be not sufficient to determine revolution speed of a fan since VAV_o_i cannot reflect the exact cooling or heating load of zone i and the volume loss of air flow to be delivered to zone i. For example, the temperature difference may not exactly reflect the total cooling or heating load of zone i or the likelihood of a change in the cooling or heating load of zone i. By assigning a weight to the openness of a damper, such as heat factors or loss factors, to control a fan that supplies conditioned air to all of the zones i, the VAV system improves its air conditioning service.

To that end, at step 504, a weighted openness for damper i ("Weighted_VAV_o_i") may be calculated by utilizing for the openness of damper i ("VAV_o_i") and a weight for the openness of damper i ("VAV_w_i"). Weighted_VAV_o_i may represent the volume of conditioned air to be delivered to each zone i while taking into consideration heat and/or loss factors.

For each zone i, Weighted_VAV_o_i is calculated as:

MathFigure 4

Weighted_VAV_o_i may be stored in a storage unit for allowing a user to configure the stored Weighted_VAV_o_i in response to any changes in the heat and the loss factors (step 506)

Steps 502-504 may be iterated until a Weighted_VAV_o_i is given to all of the dampers (for i=1 to n, i=i+1) in the VAV system (step 508).

The process then proceeds to step 510 to calculate the sum of the weighted openness of dampers i ("Weighted_VAV_sum"). The summation may represent the total volume of air flow that should be driven by a fan to all of the zones (1≤i≤n; i is an integer). Thus, the summation is calculated as:

MathFigure 5

In the above table, for example, when VAV_o₁ is 40%, VAV_o₂ is 20%, VAV_o₃ is 60%, and VAV_o₄ is 30%, Weighted_VAV_sum may be calculated as follows:

Weighted_VAV_sum = (40% × 0.10) + (20% × 0.15) + (60% × 0.45) + (30%

× 0.30) = 43%

Then, at step 512, a reference value for revolution speed of a fan may be derived from Weighted_VAV_sum in a proportional manner. The reference value for revolution speed of a fan may be revolutions per minute ("RPM"). According to one embodiment, the reference value for revolution speed of a fan may increase linearly when Weighted_VAV_sum is within a certain range of the Weighted_VAV_sum. For example, the reference value for revolution speed of a fan may be defined as:

Table 2

According to another embodiment, the reference value for revolution speed of a fan may increase stepwise when Weighted_VAV_sum is within a certain range. By increasing the reference value for revolution speed of a fan stepwise, the fan may run more stably, and noise caused by fluctuation in conditioned air flow may also decrease since the fluctuation of air flow attenuates.

For example, the reference value for revolution speed of a fan may be defined as:

Table 3

A fan may be controlled in accordance with the reference value for revolution speed of a fan (step 514). A system controller may transmit a signal indicative of the reference value for revolution speed of a fan to a fan actuator, which is operatively associated with the fan. Then, the fan actuator may rotate the fan to have the revolution speed assigned to the value of revolution speed of the fan. According to one embodiment, a fan actuator may be a BLDC motor. By using a BLDC motor as a fan actuator, the fan actuator may have a highly dynamic response to a control signal, improved speed-torque characteristic, efficient power consumption, and a widened range of variable revolution speed, etc., which helps to efficiently satisfy cooling or heating load from zones.

The systems shown in the figures may include wired communication links and/or wireless communications links for communication between components and/or with remote sources. The wireless links may be formed according to a Bluetooth communications protocol, an IEEE 802.11 protocol, an IEEE 802.16 protocol, a cellular signal, a Shared Wireless Access Protocol-Cord Access (SWAP-CA) protocol, a wireless USB protocol, or any other suitable wireless technology. Wired links may be established via Ethernet, USB technology, IEEE 1394 technology, optical technology, other serial or parallel port technology, or any other suitable wired link.

Embodiments within the scope of the present disclosure include program products comprising machine-readable media for carrying or having machine-executable instructions or data structures stored thereon. Such machine-readable media can be any available media that can be accessed by a general purpose or special purpose computer or other machine with a processor. By way of example, such machine-readable media can comprise RAM, ROM, EPROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to carry or store desired program code in the form of machine-executable instructions or data structures and which can be accessed by a general purpose or special purpose computer or other machine with a processor. When information is transferred or provided over a network or another communications connection (either hardwired, wireless, or a combination of hardwired or wireless) to a machine, the machine properly views the connection as a machine-readable medium. Thus, any such connection is properly termed a machine-readable medium. Combinations of the above are also included within the scope of machine-readable media. Machine-executable instructions comprise, for example, instructions and data which cause a general purpose computer, special purpose computer, or special purpose processing machines to perform a certain function or group of functions.

The construction and arrangement of the systems and methods as shown in the various exemplary embodiments are illustrative only. Although only a few embodiments have been described in detail in this disclosure, many modifications are possible. All such modifications are intended to be included within the scope of the present disclosure. The order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. Other substitutions, modifications, changes, and omissions may be made in the design, operating conditions and arrangement of the exemplary embodiments without departing from the scope of the present disclosure. It should be noted that although the figures may show a specific order of method steps, the order of the steps may differ from what is depicted. Also two or more steps may be performed concurrently or with partial concurrence.

Claims

A method of controlling a fan of a variable air volume ("VAV") system, the method comprising:

determining a degree of openness for at least one damper based on temperature data of at least one zone;

determining a weight for the degree of openness of the at least one damper;

using the degree of openness with the weight to ascertain a weighted degree of openness of the at least one damper ;

using the weighted degree of openness of the at least one damper to obtain a reference value for revolution speed of a fan; and

controlling the revolution speed of the fan based on the reference value.
The method of Claim 1, wherein the weighted degree of openness of the at least one damper is produced by multiplying the degree of openness with the weight.
The method of claim 2, wherein the reference value for revolution speed of the fan is determined by summing the weighted degree of openness of the at least one damper.
The method of Claims 1 to 3, wherein controlling the revolution speed of the fan comprises:

controlling the revolution speed of the fan in a stepwise way.
The method of Claim 4, wherein the fan is actuated by a brushless DC motor.
The method of Claims 1 to 3, wherein determining a weights for the degree of openness of the at least one damper comprises:

determining the weight for the degree of openness of the at least one damper based on heat factors and/or loss factors of the at least one zone.
The method of Claim 6, wherein the heat factors comprise at least one of a size of the at least one zone, a number or type of heat sources in the at least one zone, and a number, size, type or direction of windows mounted in the at least one zone.
The method of Claim 6, wherein the loss factors comprise at least one of a type, length or size of a duct extending to the at least one zone, an existence or absence of a divergence in the duct, and a type or number of diffusers located at the end of the duct.
A variable air volume ("VAV") system comprising:

at least one damper positioned to control air to at least one zone via at least one duct;

an air conditioning portion that conditions air in the at least one duct;

a fan that controls the air flow in the duct; and

a system controller that determines a degree of openness of the at least one damper based on temperature data of the at least one zone, determines a weight for the degree of openness of the at least one damper, uses the degree of openness with the weights to ascertain a weighted degree of openness of the at least one damper, uses the weighted degree of openness of the at least one damper to obtain a reference value for revolution speed of a fan, and controls the revolution speed of the fan based on the reference value.
The VAV system of Claim 9, wherein the weighted degree of openness of the at least one damper is produced by multiplying the degree of openness with the weight.
The VAV system of claim 10, wherein the reference value for revolution speed of the fan is determined by summing the weighted degree of openness of the at least one damper.
The VAV system of Claims 9 to 11, wherein the system controller controls the revolution speed of the fan in a stepwise way.
The VAV system of Claim 12, wherein the fan is actuated by a brushless DC motor.
The VAV system of Claims 9 to 11, wherein the system controller further determines the weights for the degree of openness of the at least one damper based on heat factors and/or loss factors of the at least one zone.
The VAV system of Claim 14, wherein the heat factors comprises at least one of the size of the at least one zone, a number or type of heat sources in the at least one zone, and a number, size, type or direction of windows mounted in the at least one zone.
The VAV system of Claim 14, wherein the loss factors includes at least one of a type, length or size of a duct extending to the at least zone, an existence or absence of a divergence in the duct, and a type or number of diffusers located at the end of the duct.
The VAV system of Claims 9 to 11, wherein the air conditioning portion comprises a brazed plate heat exchanger or a digital scroll compressor.
A system controller for use in a VAV system, the system controller configured to

determine a degree of openness of at least one damper based on temperature data of at least one zone;

determine a weight for the degree of openness of the at least one damper;

using the degree of openness with the weights to ascertain a weighted degree of openness of the at least one damper;

using the weighted degree of openness of the at least one damper to obtain a reference value for revolution speed of a fan; and

control the revolution speed of the fan based on the reference value.
The system controller of Claim 18, wherein the weighted degree of openness of the at least one damper is produced by multiplying the degree of openness with the weight.
The system controller of Claim 19, wherein the reference value for revolution speed of the fan is determined by summing the weighted degree of openness of the at least one damper.