Danfoss A/s

Christian Bendtsen

Frede Schmidt

Claus Thybo

Lars Mou Jessen

Kim Hansen

A method and a device for detecting an abnormality of a heat exchanger exchanging heat between a first fluid flow flowing in a conduit and a second fluid flow flowing along a flow path, said conduit and said flow path each having an inlet and an outlet, whereby the method comprises the steps of establishing at least one parameter representative of the temperature conditions of the heat exchanger, establishing a second fluid inlet temperature, establishing a parameter indicative of expected heat exchange between the heat exchanger and the second fluid, processing the heat exchanger temperature, the second fluid temperature and the parameter indicative of expected heat exchange for establishing an estimated second fluid outlet temperature, and employing the estimated second fluid outlet temperature for evaluating the heat exchange between the first and second fluids by comparing the estimated second fluid outlet temperature, or a parameter derived therefrom, with a reference value.

Method and a device for detecting an abnormality of a heat exchanger, and the use of such a device

A method for regulating a most loaded circuit of a refrigeration system is provided. Each circuit includes at least one case and an EEPR valve. At least one controller communicates with the EEPR valves for receiving signals from the circuits corresponding to operating conditions for each circuit, and for issuing command signals to the EEPR valves and compressor. The operation of each circuit is monitored and a load signal is calculated for each circuit. The load signals for each circuit are compared and the most loaded circuit is determined. The EEPR valve of the most loaded circuit is adjusted to be approximately 100 percent open and a suction pressure of the compressor is adjusted to move a circuit temperature of the most loaded circuit to a target temperature. The process of selecting and regulating the most loaded circuit is repeated after a predetermined period of time.

Method for regulating a most loaded circuit in a multi-circuit refrigeration system

Refrigeration system

Method for defrosting a refrigeration system and control apparatus for

A refrigeration system having a compressor, a condenser and an evaporator between the condenser and the compressor. A controllable valve unit at the input side of the evaporator has degrees of opening for controlling fluid flow through said evaporator. A control unit controls the degrees of opening of the valve unit. Sensors connected to the control unit and opposite ends of the evaporator detect superheat temperatures between the input and output sides of the evaporator. The control unit is operable to control the degrees of valve opening in accordance with the superheat temperatures (1) at a first greater desired opening and closing displacement rate between desired predetermined minimum and maximum values of a first range of superheat temperature values and (2) at a second opening and closing rate lesser than the first displacement rate for a second range of superheat temperature values lower than the first range of values. The second range of superheat temperature values lie within the region of 10% or less of the first range of superheat temperature values.

Refrigeration system and method of controlling a refrigeration system

Method and apparatus for controlling a prior art refrigeration system of the type having an evaporator, a variable capacity compressor arrangement, and switching apparatus between a control unit and the compressor arrangement. The compressor arrangement thereof has adding and subtracting inputs which translate input signals to respectively increase or decrease step by step the effective capacity of the compressor arrangement. The switching apparatus thereof has adding and subtracting inputs and outputs and a reset output which is made effective after each increase or decrease of the effective capacity of the compressor arrangement. The method and apparatus herein involves processing a data signal which is indicative of the temperature status of the evaporator. The data signal is compared with predetermined upper and lower temperature limits of an operating range for the evaporator and adding or subtracting temperature control signals are respectively putted when the data signal is higher or lower than those limits. The data signal has successive samples thereof examined to determined if it is rising or falling and differentiated signals are outputted depending on whether the value of a succeeding data signal is larger or smaller than the value of a preceding data signal. The adding and subtracting temperature control signals and the adding and subtracting differentiated signals are respectively ANDed and the resulting signal is applied to the adding or subtracting input of the switching apparatus. The availability of the differentiated signals for the ANDing operation are delayed for predetermined periods of time initiated by the switching apparatus.

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Sydals, Denmark

Christian Bendtsen