JPS5995603A - Controlling method of absorption cold and hot water machine - Google Patents

Abstract

PURPOSE:To reduce the integral value of dead time greatly and to improve total heat efficiency by measuring and averaging load factors and performing predictor control. CONSTITUTION:A computing element 12 for an effective mean load factor calculates an effective load factor QL from a load factor QL and a correction coefficient K.Tc/T and averages the found load factor QL simply to calculate the effective mean load factor QL'. In this case, T is the integral value of dead time, T is a predetermined period, and K is a constant. Then, it is inputted to a trailing computing element 14 for the number of machines in operation in the form of, for example, 100% for all loads. The computing element 14 operates all of (n) units of cold and hot water machines when QL'=100% or n/2 units when QL'=50%. However, a decision on whether the number of machines in operation is varied or not at the present point depends upon the value of a temperature gradient M from an inclination computing element 13 and the exit temperature of the current cold and hot water machine. Thus, the predictor control is performed to decrease the integral value Tc of dead time and the total heat efficiency is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for multi-position control of a plurality of absorption chiller/heater machines operated in parallel.

BACKGROUND ART An air conditioning system is known in which a plurality of small absorption chiller/heater machines are installed in parallel and the temperature of chilled/hot water is controlled at multiple positions by controlling the number of absorption chiller/heater machines. As shown in FIG. 1, zero absorption chiller/heater machines 1 are arranged side by side, and after their cold/hot water outlets are shared, they are connected to an air conditioner 3 via a cold/hot water pump. The common outlet pipe 2 of the absorption chiller/heater 1 is provided with a temperature detector 4, the output of which is connected to a system temperature controller 5. The output of this temperature regulator 5 is connected to a fuel control valve 6 that controls fuel supply to the absorption chiller/heater 1.

In such an air conditioning system, according to the conventional control method, the temperature controller 5 detects the temperature of cold and hot water using the temperature detector 4, compares it with a plurality of preset temperatures, and adjusts the temperature accordingly. I am trying to run an absorption chiller/heater.

FIG. 2 shows an example of the operating state of the absorption chiller/heater 1 when this system is in a cooling operating state.

In this example, the first absorption chiller/heater is controlled in two positions with an operation history of starting operation when the chilled water temperature is 6°C and stopping when the chilled water temperature is 4°C. Other absorption chiller/heaters are similarly controlled at two positions based on mutually different temperature settings, and the chilled water temperature of the entire system is set to a target value of 7°C, with a temperature control range of 4°C to 10°C. Multi-position control is used.

In the conventional control method in which the operation of each absorption chiller/heater is controlled based only on the absolute value of the chilled/hot water temperature, when the load fluctuation is large, the absorption chiller/heater also operates/operates according to the load fluctuation. This will result in repeated stops. However, since the absorption chiller/heater has a relatively large heat capacity, it takes a long time from the start of operation to reach a steady state and from the time of stopping operation to reach a stopped state. Therefore, for example, if the chilled/hot water temperature requires an additional absorption chiller/heater to start operation, the load may fluctuate before the chiller/heater reaches steady state, eliminating the need for that chiller/heater. There is. Conversely, after the absorption chiller/heater is no longer needed and stopped,
Sometimes you may need a hot and cold water machine right away. All of these operational controls are wasteful operations and cause a drop in the thermal efficiency of the entire system. Furthermore, depending on the selection of the number of multiple positions, the cold/hot water temperature tk b>excessive amount of control increases and exceeds the control temperature range, resulting in a deterioration in the quality of control.

The present invention has been made in view of the above circumstances, and aims to improve the quality of the control results and the thermal efficiency of the entire system in a method for controlling the temperature of cold and hot water at multiple positions using a plurality of absorption chiller/heaters. .

Preferred embodiments of the present invention illustrated in FIGS. 3 to 6 will be described in detail below.

The present invention does not attempt to control the operation of the absorption chiller/heater in real time, the number of which corresponds to the absolute value of the chilled/hot water temperature, as has been done in the past, but rather The system employs predictive control, which calculates the number of vehicles required to be operated in the future based on the rate. The control method will be explained below using cooling operation as an example.

First, the load factor of the absorption chiller/heater is determined from the chilled/hot water temperature detected by the temperature detector 4. The method will be explained with reference to FIG. As shown on the left side of the drawing, the outlet temperature of the water cooler/heater increases from 4°C to io''C over time.
f,” shall vary within a range of i.

This temperature signal A from the temperature sensor 4 is converted into a voltage signal, indicated by a linear υ sign B. The converted temperature signal B is then compared to a periodic sawtooth signal C having a predetermined lamp voltage.

As a result of this comparison, a pulse signal is generated that changes at each intersection of the temperature signal B and the sawtooth signal C. The midpoint of the lamp voltage of the sawtooth signal C is made to match the temperature θS (in this example, (7°C)) at the rated output point of the water cooler/heater. Therefore, the norm for a predetermined period T It becomes possible to find the ratio of the widths TH (=TH1+TH2+TH3) and consider this ratio as the load factor of the system. That is, the load factor QTJ becomes QL=T, (/T flll).

In addition, absorption chiller/heaters have an initial response, that is, a dead time from the start of operation until the rated output is produced. Therefore, the load factor must take into account this dead time (-,. This dead time T. The time also changes as a function of the outage duration, which is how long it has been since the last outage.

The cumulative value T of this dead time. The load factor that takes into account the correction factor is called the effective load factor and can be expressed as follows.

Qi = TH/T 1K -T, /T (2)
However, K is a constant.

In this way, the effective load factor calculated for each period T < Yes (
They are combined and simply averaged to obtain the effective average load factor. This effective average load factor q% becomes information that determines the number of vehicles to be operated from the present moment to the future.

On the other hand, in parallel with the calculation of the effective average load factor Qi, the temperature gradient M is determined from the temperature signal A' from the temperature detector 4. As shown in FIG. 5, the temperature gradient M can be determined from the temperature change within a certain period of time, and is expressed as M=(θ, −〇j)/(Gj −G, ). This determines the direction in which the temperature is changing (positive or negative)
and the amount of change.

Finally, based on the obtained effective average load factor I and temperature gradient M, it is determined whether the number of absorption chiller/heaters to be operated next is increased or decreased. For example, if the effective average load factor < indicates the need for additional operation of the absorption chiller/heater, and the temperature gradient M shows a negative value, it is determined that there is no need for additional operation, and conversely, M If it is positive, one additional absorption chiller/heater is controlled to be operated. However, if the absolute value of the temperature gradient M is small, the predicted temperature of cold and hot water will fall within the control temperature range L1 to L2, so as long as the temperature of the cold and hot water is within the control range, no additional operation or stop will be performed. .

Next, an example of a temperature regulator implementing the control method according to the present invention will be explained with reference to FIG.

The temperature regulator includes a temperature-voltage converter 7 that receives the temperature signal A from the temperature detector 4 and outputs a linear voltage signal B;
A sawtooth signal generator 8 generates a sawtooth signal C, a voltage comparator 9 compares the voltage signal B and the sawtooth signal C and outputs a pulse signal, and a voltage comparator 9 measures the pulse width of the pulse signal. A load factor calculator 10 that calculates the load factor QL, and a correction coefficient K from the load factor QL and correction coefficient calculator 11.
-T.

An effective average load factor calculator 12 calculates the effective load factor from /T and further calculates the effective average load factor.

Gradient calculator 13 that outputs temperature gradient M from temperature signal A'
and an operating unit number calculation unit 14 that determines the number of operating units from the effective average load factor Q and temperature gradient M.

The voltage comparator 9 outputs a pulse signal according to the method shown in FIG. This pulse signal is used, for example, as a gate signal for a gate circuit that supplies a clock signal to a counter in the load factor calculator IO. The counter counts the pulse width TH of the pulse signal every cycle T. Next, the load factor Q is determined for each cycle by calculating the divisor of TH/T.
L is output.

The correction coefficient calculation unit 11 calculates the Indy/Kill response time of the water cooler/heater started operating within a predetermined period based on the data from the operating number calculation unit 14, and further calculates -To/T as a correction coefficient. The initial response varies depending on the capacity of each water chiller/heater and the period of time it has been stopped before starting operation.

The effective average load factor calculator 12 calculates the load factor Q1 and the correction coefficient K.
- Calculate the effective load factor Q1 of the above formula (2) from To/T, and simply average the obtained effective load factor < to calculate the effective average load factor Q.
Z is calculated and input to the next operation number calculator 14 in the form of 100% at full load, for example.

The operation number calculator 14 calculates that if Q = 100%, all n cold water machines are operated, and if it is 50%, n/2 units are operated. However, the decision as to whether or not to change the number of operating units at this point in time depends on the value of the temperature gradient M from the slope calculator 13 and the current water cooler/heater outlet temperature. For example, if the outlet temperature is close to the target temperature θ8=7°C and the absolute value of the temperature gradient M is within the predetermined range, the current Even if data is obtained to increase or decrease the number of water coolers/heaters, the current operating conditions will not be changed. If you do not change this (even if it is within a certain period in the future), the set temperature range is 4 to 1.
This is because the temperature is within 0°C. However, if the outlet temperature deviates from the set temperature range within the above fixed period from the current outlet temperature and the temperature gradient M calculated based on past data, the absolute value of the temperature gradient M will be small. However, the number of water coolers and hot water machines will be increased or decreased.

Note that the operation number calculator 14 calculates that n absorption chiller/heater machines operated in parallel have the same capacity, and when Q = 50%, n/
Although we have explained the case where two absorption chillers/heaters are operated, if the capacity of each absorption chiller/heater is different, the corresponding output percentage will be assigned to each, and the same applies if the capacity of one absorption chiller/heater can be varied. Assigned. Of course, since the effective average load factor received from the effective average load factor calculator 12 is a continuous quantity, it is converted into a discontinuous quantity according to the capacity and output.

Conventionally, in multi-position feedback control based on the absolute value of temperature, the absorption chiller/heater has to be started and stopped many times (when the load is fluctuating, the dead time due to the individual response is large). However, according to the present invention, since the load factor itself is measured and averaged to perform predictive control, the integrated value of dead time is significantly reduced and the total thermal efficiency is reduced. This improves the thermal efficiency of the system.

Furthermore, reducing the dead time also reduces the control temperature range, and the controlled temperature does not deviate significantly from the set temperature range (thus, the quality of control can be improved).

The present invention has been described in detail with respect to its preferred embodiments, but
The invention is not limited to this particular embodiment (
Numerous changes and modifications are possible without departing from the spirit of the invention. For example, similar control is possible during heating operation.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing an air conditioning system, Fig. 2 is a diagram to explain conventional multi-position temperature control, Fig. 3 is an explanatory diagram for determining the load factor, and Fig. 4 is an explanatory diagram of the correction coefficient. , FIG. 5 is an explanatory diagram for determining the temperature gradient, and FIG. 6 is a diagram showing an example of the configuration of a temperature regulator for carrying out the method of the present invention. 1. Absorption chiller/heater, 2. Common outlet pipe, 3. Air conditioner, 4. Temperature detector, 5. Temperature controller, 6. Fuel control valve, 7. Temperature-voltage conversion. 8...Sawtooth image signal generator, 9...Voltage comparator, lO...Load factor calculator, 11...Correction coefficient calculator, 12...Effective average load factor calculator, 13...Slope calculator , 14...operating unit number calculator,
A...Temperature signal, B...Voltage temperature signal, C...Sawtooth wave signal, D...Pulse signal, M...Temperature gradient, QL.
・Load factor, caW ・・Effective average load factor.

Claims (1)

[Claims] In a method of installing multiple absorption chiller/heaters in parallel and controlling the chilled/hot water temperature at their common outlet or inlet at multiple positions, the chilled/hot water temperature is detected and a predetermined time is determined based on the detected chilled/hot water temperature. Calculate the average load factor for each time period, calculate the effective average load factor from this average load factor, taking into account the initial response time of the absorption chiller/heater that is about to start operation next, and The temperature gradient for a predetermined period of time is calculated from the cold and hot water temperature, and the optimum number of operating units at the present time is calculated by qualitative logical product of the effective average load factor and the temperature gradient. How to control a hot and cold water machine.