1. Field of the Invention
The present invention relates to an absorption refrigerator (including an absorption water chilling/heating machine), which is provided with two types of heat sources for generating refrigerant vapor by heating an absorption liquid.
2. Detailed Description of the Prior Art
An absorption refrigerator has been known, which heats an absorption liquid by use of high-temperature generated by combustion of natural gas, petroleum, or the like and exhaust heat from a cogeneration system or the like to evaporate and separate a refrigerant from the absorption liquid, and thus generates refrigerant vapor and a concentrated absorption liquid.
Another absorption refrigerator also has been known, in which exhaust heat supplied from both of exhaust hot water and exhaust gas of a cogeneration system using a gas engine or the like is utilized as heat sources.
In both cases, one heat source is preferentially used in accordance with a utilization form of heat of a user. In the light of an efficient use of heat, it is necessary that heat from a heat source to be preferentially used can be surely used.
In Japanese Patent Application 2000-074173, the inventors have proposed a control method, which sets two different values as temperature setting values of cold water cooled and supplied in an evaporator. The method controls a heating amount by one heat source based on one set temperature value, and controls a heating amount by the other heat source based on the other set temperature value.
By the proposed control method in Japanese Patent Application 2000-074173, the heat sources can be used in accordance with priorities. However, when the heating amount of the absorption fluid is controlled by means of a PID control setting a wide proportional band or a long integral time, immediate change of loads sometimes causes a disadvantage that the cold water is excessively cooled during the time of closing a fuel supply valve or confirming a fully-closed state thereof, and the apparatus is abnormally stopped. Accordingly, a control method without causing such disadvantage needs to be provided, which has been a problem to be solved.
The present invention solves the foregoing subjects of the prior arts by providing the following concrete means.
A first method of controlling an absorption refrigerator, which comprises the steps of: controlling a heating amount Q1 of an absorption liquid by a heat source A by means of a control using a first set temperature value T1 of cold water supplied from an evaporator as a reference value, the heat source A being to be preferentially used; controlling a residual heating amount Q2 of the absorption liquid by a heat source B by means of a control using a second set temperature value T2 higher than the first set temperature value T1 as a reference value; releasing heat of the refrigerant vapor for condensation in a condenser, the refrigerant vapor being evaporated and separated from the absorption liquid by heating the absorption liquid; evaporating the condensed liquid refrigerant in the evaporator; and supplying cold water cooled in the evaporation of the refrigerant in the evaporator to a load to perform a cooling operation such as air conditioning; wherein when the heating amount Q2 of the absorption liquid is continuously a minimum value for a predetermined time, the heating amount Q2 of the absorption liquid is forcibly controlled to be zero and the heating amount Q1 of the absorption liquid is controlled by means of the control using the first set temperature value T1 as a reference value, and wherein when the heating amount Q1 of the absorption liquid is continuously a maximum value for a predetermined time, the heating amount Q1 of the absorption liquid is forcibly controlled to be the maximum value and the heating amount Q2 of the absorption liquid is controlled by means of the control using the second set temperature value T2 as the reference value.
In the first method, a second method is provided, wherein in a state that the heating amount Q1 of the absorption liquid is forcibly controlled to be the maximum value, when a temperature T of the cold water supplied from the evaporator becomes lower than the second set temperature value T2, the control of the heating amount Q1 of the absorption liquid using the first set temperature value T1 as the reference value is started again.
In the first method, a third method is provided, wherein in a state that the heating amount Q2 of the absorption liquid is forcibly controlled to be zero, when a temperature T of the cold water supplied from the evaporator exceeds a third set temperature value T3 higher than the second set temperature value T2, the control of the heating amount Q2 of the absorption liquid using the second set temperature value T2 as the reference value is started again.