Methods and systems for detecting and recovering from control instability caused by impeller stall in a chiller system are provided. In one embodiment, an impeller stall detection and recovery component of a chiller control unit calculates a control error signal frequency spectrum for an evaporator leaving water temperature, determines whether a high frequency signal content of the control error signal frequency spectrum exceeds acceptable limits, and adjusts a surge boundary control curve downward by a predetermined incremental value in order to resolve instability caused by impeller stall.

A method for controlling a vapor compression system during start-up is disclosed. The rate of change, ΔT.sub.1, of the temperature of refrigerant entering the evaporator, and the rate of change, ΔT.sub.2, of the temperature of refrigerant leaving the evaporator are compared. Based on the comparing step, a refrigerant filling state of the evaporator is determined. The opening degree of the expansion device is then controlled according to a first control strategy in the case that it is determined that the evaporator is full or almost full, and according to a second control strategy in the case that it is determined that the evaporator is not full. Thereby it is ensured that a maximum filling degree of the evaporator is quickly reached, without risking that liquid refrigerant passes through the evaporator.

The present disclosure discloses a liquid cooler having separable and portable components. The liquid cooler has a liquid cooling section and a refrigerating system section. In an operative liquid cooling configuration, the components present in the liquid cooling section and the refrigerating system section are connected with each other with a first and second releasing coupler. In an operative defrosting configuration, the components of present in the liquid cooling section and the refrigerating system section are separated with each other by releasing the first and second releasing coupler and hence are easily portable. The separated liquid cooling section and the refrigerating system section enables easy periodic maintenance or replacement of faulty components in less time, labor and cost. Further, the liquid cooler is powered by power received from power mains or by power storage device such as battery.

The present disclosure relates to a method for controlling a level of superheat during a pump mode of operation of a refrigeration system, wherein the refrigeration system can operate in either the pump mode or a compressor mode, and has an electronically controlled expansion valve (EEV). A controller obtains a stored, predetermined pump differential pressure range able to be produced by a pump of the system. The controller also obtains a stored, predetermined superheat range, and detects a superheat level. When the detected superheat level is outside of the superheat temperature range, the controller commands adjusting at least one of the EEV and a speed of the pump based on whether the detected superheat level is above or below the superheat range, and whether a current pump differential pressure is above or below the predetermined pump differential pressure range.

Methods and systems for controlling a chiller system to achieve control stability while maintaining optimum efficiency. Particularly, methods and systems for controlling a centrifugal compressor speed and an inlet guide vane position that establishes three distinct regions in the control path: (i) during initial unloading from full load, the inlet guide vane position is kept at a fully open position while the centrifugal compressor speed is changed to achieve the desired cooling capacity; (ii) between an inflection point and a transition point, keeping the centrifugal compressor speed constant while the inlet guide vane position is changed to achieve the desired cooling capacity; and (iii) between the transition point and zero cooling capacity, changing both the inlet guide vane position and the centrifugal compressor speed to achieve the desired cooling capacity.

A system for producing a heat source for heating or electricity, using medium/low-temperature waste heat includes: an absorption-type heat pump (100) supplied with a driving heat source and heat source water to heat a low-temperature heat medium; a regenerator heat exchange unit (210) for supplying a regenerator (110) with a driving heat source using waste heat; an evaporator heat exchange unit (220) for supplying an evaporator with heat source water; a heat medium circulation line (310) for circulating a heat medium; a generation unit (400) branching off from the heat medium circulation line (310) and producing electricity; a heat production unit (500) branching off from the heat medium circulation line (310) and supplying a heat-demanding place with a heat source for heating; and a switching valve unit (600) for controlling the flow of heat medium supplied the generation unit (400) or the heat production unit (500).

A method for preventing formation of droplets in a heat exchanger, in which a second medium transfers heat to a first. The method is performed by a controller which receives different temperature values (T.sub.1, T.sub.2, T.sub.3) and a pressure (P) value to be used for calculating a boiling point temperature value (T.sub.B) and determining a first temperature difference (ΔT.sub.1) and a second temperature difference (ΔT.sub.2). Generating a flow control signal, for controlling the flow of the first medium into the heat exchanger, based on the first temperature difference (ΔT.sub.1), the second temperature difference (ΔT.sub.2) and the first temperature value T.sub.1 and sending the flow control signal to a regulator device for controlling the flow of the first medium in the heat exchanger.

A temperature control system according to one embodiment includes: a refrigeration apparatus in which a compressor, a condenser, an expansion valve and an evaporator are connected in this order for circulating a refrigerant; a fluid circulation apparatus that causes a fluid to be heat-exchanged in the evaporator, then sends the fluid to a temperature control object, and again causes the fluid having passed through the temperature control object to be heat-exchanged in the evaporator, the fluid circulation apparatus having a heater at a position downstream of the temperature control object and upstream of the evaporator; and a control apparatus. The control apparatus activates the heater to heat the fluid by the heater, when the fluid circulation apparatus has become in a no-load operation state or a no-load-operation transition operation state, wherein the no-load operation state is a state in which the fluid and the temperature control object do not heat-exchange, the no-load-operation transition operation state is a state that is in transition to the no-load operation state.

The purpose of the present invention is to achieve stable operation when using a low pressure, low GWP refrigerant. In the present invention, a control device (16) is provided with an estimation unit (31), a determination unit (32), and an activation control unit (33). The estimation unit (31) estimates the amount of air entering using a degree of influence of air entering, which represents the ease with which air enters determined by the structure of the chiller, and a variable obtained by a function including pressure as a parameter. The determination unit (32) determines whether a total value for the amount of air entering is greater than or equal to a preset tolerance value. The activation control unit (33) activates a bleed device when the total value of the amount of air entering is equal to or greater than the tolerance value.

A method for controlling operation of a refrigeration system (1), including one or more refrigeration entities (4), is disclosed. Each entity controller (7) obtains a measure for an error value between the measured value of a compressor control parameter and a setpoint value (8) for the compressor control parameter, and each entity controller (7) adjusts a refrigeration load of the corresponding refrigeration entity (4) to correspond to a cooling capacity of the compressor(s) (2), and in accordance with the obtained measure for an error value.