Control of a pump to optimize heat transfer

Patent metadata

Field	Value
Publication number	US-2016238261-A1
Application number	US-201315029309-A
Country	US
Kind code	A1
Filing date	Oct 14, 2013
Priority date	Oct 14, 2013
Publication date	Aug 18, 2016
Grant date	—

Abstract

The present invention relates to a method for controlling a pump for feeding fluid (F) into a heating system ( 1000 ). The heating system has a hot fluid tank (HFT) receiving fluid from an associated fluid reservoir line ( 5 ) with an incoming fluid mass flow rate (dm cw /dt). A pump (P) receives fluid from the line, and pumps the received fluid with amass flow rate (dm c /dt). A heat exchanging unit (HX) transfers heat (Q) to the fluid (F) from a medium (R). The transferred heat (Q) is maximized by controlling the pump (P 1 ) in response to this information indicative of the transferred heat (Q), the fluid mass flow rate delivered by the pump thereby having a minimum as a function of the incoming fluid mass flow rate (dm cw /dt) when maximizing the transferred heat. The invention provides significantly improved heat transfer to the fluid and power savings for the pump. The invention also relates to a heating system, e.g. a heat pump system.

First claim

1 . A method for controlling a pump for feeding fluid into a heating system, the heating system comprising:
a hot fluid tank HFT, the hot fluid tank receiving fluid from an associated fluid reservoir line with an incoming fluid mass flow rate, a pump, the pump also receiving fluid from the said fluid reservoir line, and pumping received fluid with a variable fluid mass flow rate, the pump and the hot fluid tank receiving fluid from a common junction on said associated fluid reservoir line, and a heat exchanging unit, the heat exchanging unit receiving fluid from the associated fluid reservoir line driven by the pump, and transferring heat to the fluid from a medium, the method comprises providing information indicative of a transferred heat in the heat exchanging unit to the fluid, wherein the said transferred heat is maximized by controlling the pump in response to said information indicative of the transferred heat to the fluid at least within a finite interval of the incoming fluid mass flow rate, a fluid mass flow rate delivered by the pump thereby having a minimum as a function of the incoming fluid mass flow rate when maximizing the transferred heat in said finite interval.

2 - 21 . (canceled)

22 . The method according to claim 1 , wherein the transferred heat is also being maximized outside of said finite interval by operating the pump at a maximum of the fluid mass flow rate deliverable by the pump.

23 . The method according to claim 1 , wherein controlling the pump at a maximum of the transferred heat—at a lower end of said interval—is resulting in the fluid mass flow rate decreasing as a function of the incoming fluid mass flow rate, and a resulting fluid mass flow rate being larger than the incoming fluid mass flow rate thereby resulting in a back flow of heated fluid from the hot fluid tank through the said common junction.

24 . The method according to claim 23 , wherein controlling the pump at said maximum of the transferred heat—at a higher end of said interval—is resulting in an increasing fluid mass flow rate as a function of the incoming fluid mass flow rate.

25 . The method according to claim 24 , wherein controlling the pump—at the higher end of said interval—is resulting in an increasing mass flow rate being substantially the same as the incoming fluid mass flow rate.

26 . The method according to claim 1 , wherein providing information indicative of a transferred heat in the heat exchanging unit to the fluid is performed based on input from at least two temperature sensors at an inlet and/or an outlet of the heat exchanging unit at a primary side and/or at a secondary side of said heat exchanging unit.

27 . The method according to claim 1 , wherein providing information indicative of a transferred heat in the heat exchanging unit to the fluid is performed based on input from one or more temperature sensors at an inlet of and/or within the hot fluid tank.

28 . The method according to claim 1 , wherein providing information indicative of a transferred heat in the heat exchanging unit to the fluid is performed based on input from one or more flow meters.

29 . The method according to claim 1 , wherein providing information indicative of a transferred heat in the heat exchanging unit to the fluid is performed based on input from one or more flow meters for measuring the incoming fluid mass flow rate from said fluid reservoir line, and a medium mass flow rate through the primary side of the heat exchanging unit.

30 . The method according to claim 1 , wherein providing information indicative of a transferred heat in the heat exchanging unit to the fluid is performed based on input from one or more flow meters for measuring the incoming fluid mass flow rate from said fluid reservoir line, or a medium mass flow rate through the primary side of the heat exchanging unit.

31 . The method according to claim 28 , wherein the pump is applied as an indirect flow meter by utilising characteristics about the pump and one or more applied control parameters for operating the pump.

32 . The method according to claim 1 , wherein providing information indicative of a transferred heat in the heat exchanging unit to the fluid is performed based on input from one or more parameters related to a power consumption of the heating system.

33 . The method according to claim 1 , wherein providing information indicative of a transferred heat in the heat exchanging unit to the fluid is performed based on input from one or more parameters related to a power consumption of a compressor compressing a refrigerant in a heat pump system.

34 . The method according to claim 26 , wherein a maximization of transferred heat is performed in a feed-forward control regime by solving for the mass flow rate of the pump;
Q=f ( T cw ,T t ,T h ,dm c /dt,dm h /dt,dm cw /dt,U,A,cp c ,cp h ) wherein: T cw is an estimated, or measured, temperature of the incoming fluid, T t is an estimated, or measured, temperature of fluid in the hot fluid tank, T h is an estimated, or measured, temperature of the medium at the inlet of the heat exchanging unit, dm c /dt is the mass flow rate delivered by the pump, dm h /dt is the mass flow rate of the medium at the inlet of the heat exchanging unit, dm cw /dt is the estimated, or measured, mass flow rate of the incoming fluid, U is a heat transfer coefficient per area of the heat exchanging unit, A is an effective area for a heat transfer of the heat exchanging unit, cp c is a heat capacity of the fluid, and cp h is a heat capacity of the medium.

35 . The method according to claim 26 , wherein a maximization of transferred heat is performed in a continuous feedback control regime by iteratively changing the mass flow rate of the pump and monitoring a corresponding effect on the transferred heat.

36 . The method according to claim 26 , wherein a maximization of transferred heat is performed in a logical feedback control regime by either operating the pump at the maximum rated mass flow rate, or operating the pump at a mass flow rate equal to the incoming fluid flow mass rate, the incoming fluid flow mass rate being estimated by either a flow meter in a fluid inlet line, and/or the flow direction being indirectly estimated based on a temperature sensor in between the said common junction and the hot fluid tank by comparison with the temperature of the incoming fluid.

37 . The method according to claim 26 , wherein a maximization of transferred heat is performed by changing the mass flow rate of the pump and monitoring a corresponding effect on the transferred heat by averaging over a period of time sufficient to reach a steady state of transferred heat with respect to the mass flow rate of the pump.

38 . The method according to claim 1 , wherein the heating system comprises a heat pump system, the heat pump system comprising a refrigerant line with said heat exchanging unit, a second, and a third exchanging unit being interconnected,
the heat exchanging unit receiving fluid from the pump, and performing sub-cooling of a refrigerant so as to transfer heat to the fluid, the second exchanging unit performing super-heating of said refrigerant so as to transfer heat to the fluid, and the third exchanging unit receiving the refrigerant from said second exchanging unit and performing condensation of said refrigerant, and conveying the cooled refrigerant to the heat exchanging unit.

39 . The method according to claim 1 , wherein the heating system com

Assignees

• Grundfos Holding As

Inventors

• Lyhne Casper Hillerup

Classifications

• Y02B10/20

  Solar thermal · CPC title

• F24D19/1009 Primary

  for central heating · CPC title

• F24D19/1012 Primary

  by regulating the speed of a pump · CPC title

• F24D19/1054

  the system uses a heat pump · CPC title

• F24D19/1057

  the system uses solar energy · CPC title