Method and a device for detecting flash gas
AssigneeDanfoss A/S
InventorsClaus Thybo, Bjarne Dindler Rasmussen, Steen Lauridsen, Vagn Helberg
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Abstract
A method and a device for detecting flash gas in a vapor-compression refrigeration or heat pump system comprising a compressor, a condenser, an expansion device, and an evaporator interconnected by conduits providing a flow path for a refrigerant, by determining a first rate of heat flow of a heat exchange fluid flow across a heat exchanger of the system and a second rate of heat flow of the refrigerant across the heat exchanger, and using the rates of heat flow for establishing an energy balance from which a parameter for monitoring the refrigerant flow is derived, to thereby provide early detection of flash gas with a minimum number of false alarms.
Claims19
A flash gas detection device for a vapour-compression refrigeration or heat pump system comprising a compressor, a condenser, an expansion device, and an evaporator interconnected by conduits providing a flow path for a refrigerant, wherein the device comprises:
- means for determining a first rate of heat flow of a heat exchange fluid flow across a heat exchanger of the system and a second rate of heat flow of the refrigerant across the heat exchanger, and using the rates of heat flow for establishing an energy balance from which a residual for monitoring the refrigerant mass flow is derived;
- and
- evaluation means for evaluating the refrigerant mass flow, and providing an output signal indicating the presence or absence of flash gas, based on the residual,
- wherein the means for determining the second rate of heat flow uses inputs from means for sensing absolute refrigerant pressure before and after the expansion device, means for establishing an opening passage or opening period of the expansion device, and means for storing a value representing a flow characteristic of the expansion device, without requiring measurement of refrigerant temperature at the expansion device entry and exit.
A flash gas detection device for a vapour-compression refrigeration or heat pump system comprising a compressor, a condenser, an expansion device, and an evaporator interconnected by conduits providing a flow path for a refrigerant, wherein the device comprises:
- means for determining a first rate of heat flow of a heat exchange fluid flow across a heat exchanger of the system and a second rate of heat flow of the refrigerant across the heat exchanger, and using the rates of heat flow for establishing an energy balance from which a residual for monitoring the refrigerant mass flow is derived;
- and
- evaluation means for evaluating the refrigerant mass flow, and providing an output signal indicating the presence or absence of flash gas, based on the residual,
- wherein the means for determining the second rate of heat flow uses inputs from means for sensing absolute refrigerant pressure before and after the expansion device, means for establishing an opening passage or opening period of the expansion device, and means for storing a value representing a flow characteristic of the expansion device, and determines the refrigerant mass flow according to the equation:
- {dot over (m)}ref=kexp·(Pcon−Pref,out)·OP
- where
- {dot over (m)}ref:
- refrigerant mass flow
- kexp:
- value representing the flow characteristic of the expansion device
- Pcon:
- absolute refrigerant pressure before the expansion device
- Pref,out:
- absolute refrigerant pressure after the expansion device
- OP:
- opening passage or opening period of the expansion device,
- without requiring measurement of refrigerant temperature at the expansion device entry and exit.
A flash gas detection device for a vapour-compression refrigeration or heat pump system comprising a compressor, a condenser, an expansion device, and an evaporator interconnected by conduits providing a flow path for a refrigerant, wherein the device comprises:
- means for determining a first rate of heat flow of a heat exchange fluid flow across a heat exchanger of the system and a second rate of heat flow of the refrigerant across the heat exchanger, and using the rates of heat flow for establishing an energy balance from which a residual for monitoring the refrigerant mass flow is derived;
- and
- evaluation means for evaluating the refrigerant mass flow, and providing an output signal indicating the presence or absence of flash gas, based on the residual,
- wherein the means for determining the second rate of heat flow uses inputs from means for sensing absolute refrigerant pressure before and after the expansion device, means for establishing an opening passage or opening period of the expansion device, and means for storing a value representing a flow characteristic of the expansion device, and the evaluation means provides the output signal indicating the presence of the flash gas in case the time average of the residual is less than zero.
Dependencies are inferred from the claim text.