HVAC Hydronic System with Split Buffer Tank for Zero-Mixing System Operation

Abstract

The present invention relates to HVAC-systems operating under new ZERO-MIXING (ZM) water flow condition as innovative way to promote consistent highly energy efficient performance on SOURCE-heating/cooling thermal production and BUILDING's system distribution (FIG. 1). ZM technology is applicable; but not limited, to large-residential, commercial, institutional, and industrial facilities. Current state on HVAC technology, for system hydronics loop-flow, do not provide flows temperature segregation mechanisms between heating/chiller-plants hot/cold water supply and warmer water system returns. The result, a system that continuously operates at WATER MIXING conditions that impair equipment efficiency and output, and therefore, overall system energy performance.

1 . A hydronic HVAC system comprising:
 a heating/cooling source (B 1 -B 2 /CH) for heating or cooling a working fluid;   a split-buffer tank (SBT) comprising a vessel ( 1 ) in which there is contained a separation disk ( 2 ) that divides an interior space of the vessel into separate supply and return chambers (SC, RC) on opposing sides of said separation disk for respective holding of differently temperatured volumes of the working fluid in isolated fashion from another within said separate supply and return chambers, said separation disk ( 2 ) being freely movable back and forth in an axial direction of the vessel to vary the relative sizes of said supply and return chambers and thereby accommodate volumetric variation between said differently temperatured volumes of the working fluid;   a primary fluid loop and a primary pumping system (P 1 , P 2 ) installed therein in a manner operable to pump the working fluid through the heating/cooling source from the return chamber of the split buffer tank to the supply chamber of the split buffer tank;   a secondary fluid loop and a secondary pumping system (P 3 ) installed therein in a manner operable to pump the working fluid from the supply chamber of the split buffer tank to at least one heating/cooling unit (FC 1 , FC 2 , FC 3 , HP, MUA, DHW) that uses the working fluid for heating/cooling purposes, said secondary fluid loop comprising at least one return line through which the working fluid is returnable from at least one heat/cooling unit to the return chamber of the split buffer tank;   at least one control valve (CV 1 , CV 2 , CV 3 ) installed in said at least one return line, said at least one control valve being settable into a plurality of different operating states, including at least a recirculation state operable to recirculate said working fluid back through said secondary fluid loop, and a bypass state operable to return said working fluid back to the return chamber of the split buffer tank; and   a control system configured to operate the secondary pumping system, thereby causing circulation of the working fluid through the secondary fluid loop, and during said circulation of the working fluid through the secondary fluid loop, operate the at least one control valve by performing at least the following steps on an ongoing basis:
 (a) monitoring a fluid return temperature (T SWR ) of the working fluid in said at least one return line; 
 (b) determine whether the fluid return temperature (I SWR ) fulfills a targeted minimum temperature differential (ΔT) relative to an output temperature setpoint (T SP ) of the heating/cooling source to achieve operating efficiency thereof in an optimal range; 
 (c) when the return temperature of the working fluid fulfills said targeted minimum temperature differential, set or maintain said at least one control valve in the bypass state; and 
 (d) when the return temperature of the working fluid does not fulfill said targeted minimum temperature differential, set or maintain said at least one control valve in the recirculation state. 
   
     
     
         2 . The system of  claim 1  wherein said heat/cooling source is a heating source (B 1 -B 2 ), step (b) comprises determining whether the fluid return temperature fulfills the targeted temperature differential by checking whether the fluid return temperature is less than a control valve setpoint value, step (c) comprises setting or maintaining said at least one control valve in the bypass state when the fluid return temperature is less than the control valve setpoint value, and step (d) comprises setting or maintaining said at least one control valve in the recirculation state when the fluid return temperature is greater than the control valve setpoint value. 
     
     
         3 . The system of  claim 1  wherein said heat/cooling source is a cooling source (CH), step (b) comprises determining whether the fluid return temperature fulfills the targeted temperature differential by checking whether the fluid return temperature is greater than a control valve setpoint value, step (c) comprises setting or maintaining said at least one control valve in the bypass state when the fluid return temperature is greater than the control valve setpoint value, and step (d) comprises setting or maintaining said at least one control valve in the recirculation state when the fluid return temperature is less than the control valve setpoint value. 
     
     
         4 . The system of any  claim 1  wherein the control system is configured to variably adjust the targeted minimum temperature differential. 
     
     
         5 . The system of  claim 4  wherein the control system is configured to variably adjust the targeted minimum temperature differential based at least partly on an outdoor temperature. 
     
     
         6 . The system of  claim 2  wherein the control system is configured to variably adjust the control valve setpoint value. 
     
     
         7 . The system of  claim 6  wherein the control system is configured to variably adjust the control valve setpoint value based at least partly on an outdoor temperature. 
     
     
         8 . The system  claim 1  wherein the secondary fluid loop comprises a plurality of fluid circuits through which the working fluid is respectively delivered to a plurality of different heating/cooling equipment types (HP, MUA, DHW), the at least one return line comprises a plurality of respective return lines each belonging to a respective one of the fluid circuits, the at least one control valve comprises a plurality of respective control valves (CV 1 /CV 1 ′, CV 2 , CV 3 ) each installed in a respective one of said plurality of return lines, and the control system is configured to monitor a respective fluid return temperature in each of said return lines, and to control the respective control valve of each return line based on the respective fluid return temperature in said return line. 
     
     
         9 . The system of  claim 8  wherein each respective control valve (CV 1 , CV 2 , CV 3 ), in the recirculation state thereof, is operable to recirculate the working fluid back through a same one of the fluid circuits in which said respective control valve is installed. 
     
     
         10 . The system of  claim 8  wherein at least one of the respective control valves (CV 1 ′), in the recirculation state thereof, is operable to recirculate the working fluid through a different one of the fluid circuits that that in which said respective control valve is installed. 
     
     
         11 . The system of  claim 10  wherein the heating/cooling source is a heating source (B 1 -B 2 ), and said at least one of the respective control valves is a first control valve (CV 1 ′) installed in the respective return line of a first fluid circuit whose respective fluid return temperature is greater than a second fluid circuit into which the first control valve is operable, in the recirculation state thereof, to recirculate the working fluid. 
     
     
         12 . A method of controlling hydronic heating or cooling, said method comprising:
 having hydronic HVAC system comprising:
 a heating/cooling source (B 1 -B 2 /CH) for heating or cooling a working fluid; 
 a split-buffer tank (SBT) comprising a vessel ( 1 ) in which there is contained a separation disk ( 2 ) that divides an interior space of the vessel into separate supply and return chambers (SC, RC) on opposing sides of said separation disk for respective holding of differently temperatured volumes of the working fluid in isolated fashion from another within said separate supply and return chambers, said separation disk ( 2 ) being freely movable back and forth in an axial direction of the vessel to vary the relative sizes of said supply and return chambers and thereby accommodate volumetric variation between said differently temperatured volumes of the working fluid; 
 a primary fluid loop in which the heating/cooling source is fluidly connected between the supply and return chambers of the split buffer to receive said working fluid from the return chamber and heat/cool said working fluid, before loading thereof into the supply chamber of the split buffer; 
 a secondary fluid loop in which at least one heating/cooling unit (FC 1 , FC 2 , FC 3 , HP, MUA, DHW) is fluidly connected between the supply and return chambers of the split buffer to receive said working fluid from the supply chamber and use said working fluid to address a heating/cooling load, before returning said working fluid to the return chamber; 
   during circulation of the working fluid through the secondary fluid loop, performing the following steps:
 (a) monitoring a fluid return temperature (T SWR ) of the working fluid in the secondary fluid loop at a location downstream of the at least one heating/cooling unit and upstream of the return chamber of the split buffer; 
 (b) determining whether the fluid return temperature fulfills a targeted minimum temperature differential (ΔT) relative to an output temperature setpoint (T SP ) of the heating/cooling source to achieve operating efficiency thereof in an optimal range; 
 (c) when the fluid return temperature (T SWR ) fulfills said targeted minimum temperature differential (ΔT), returning the working fluid to the return chamber of the split buffer; and 
 (d) when the fluid return temperature does not fulfill said targeted minimum temperature differential (ΔT), recirculating the working fluid back through the secondary loop. 
   
     
     
         13 . The method of  claim 12  wherein said heat/cooling source is a heating source (B 1 -B 2 ), step (b) comprises determining whether the fluid return temperature fulfills the targeted temperature differential by checking whether the fluid return temperature is less than a control valve setpoint value, step (c) comprises returning the working fluid to the return chamber of the split buffer when the fluid return temperature is less than the control valve setpoint value, and step (d) comprises recirculating the working fluid back through the secondary loop when the fluid return temperature is greater than the control valve setpoint value. 
     
     
         14 . The method of  claim 12  wherein said heat/cooling source is a cooling source (CH), step (b) comprises determining whether the value of the fluid return temperature fulfills the targeted temperature differential by checking whether the fluid return temperature is greater than a control valve setpoint value, step (c) comprises returning the working fluid to the return chamber of the split buffer when the fluid return temperature is greater than the control valve setpoint value, and step (d) comprises recirculating the working fluid back through the secondary loop when the fluid return temperature is less than the control valve setpoint value. 
     
     
         15 . The method of  claim 12  wherein comprising, over time, variably adjusting the targeted minimum temperature differential. 
     
     
         16 . The method of  claim 15  comprising, over time, variably adjusting the targeted minimum temperature differential based at least partly on an outdoor temperature. 
     
     
         17 . The method of  claim 13  comprising, over time, variably adjusting the control valve setpoint value. 
     
     
         18 . The method of  claim 17  comprising, over time, variably adjusting the control valve setpoint value based at least partly on an outdoor temperature. 
     
     
         19 . The method of  claim 12  wherein the secondary fluid loop comprises a plurality of fluid circuits through which the working fluid is respectively delivered to a plurality of different heating/cooling equipment types (HP, MUA, DHW), and the method comprises returning or recirculating working fluid from each of said fluid circuits based on a respective fluid return temperature measured therein. 
     
     
         20 . A split buffer tank (SBT) for storing temperature-distinct volumes of working fluid therein as a buffer between primary and secondary fluid loops of a hydronic heating/cooling system, said split buffer tank comprising:
 a vessel ( 1 ) having first and second ends that are spaced apart from one another in an axial direction of the vessel, and that are situated oppositely of one another across an interior space of the vessel delimited between said first and second ends, and a circumferential wall that spans axially between the first and second ends of the vessel and closes circumferentially around the interior space thereof;   a separation disk ( 2 ) that is contained in said vessel and divides the interior space thereof into separate supply and return chambers (SC, RC) on opposing sides of said separation disk for respective holding of differently temperatured volumes of the working fluid in isolated fashion from another within said separate supply and return chambers, said separation disk ( 2 ) being movable back and forth in the axial direction of the vessel to vary the relative sizes of said supply and return chambers and thereby accommodate volumetric variation between said differently temperatured volumes of the working fluid;   a shaft spanning across the interior space of the vessel in the axial direction thereof, said shaft penetrating through the first and second ends of the vessel and also through the separation disk, which is slidably disposed around said shaft for sliding movement back and forth along the shaft;   a supply chamber inlet installed on the first end of the vessel to receive the working fluid from one or more heating/cooling sources in a primary loop of the hydronic heating/cooling system, said supply chamber inlet opening into the supply chamber of the vessel and also receiving a first end portion of the shaft that penetrates through the first end of the vessel, thereby externally supporting said first end portion of the shaft outside the vessel;   a return chamber inlet installed on the second end of the vessel to receive the working fluid back from a secondary loop of the hydronic heating/cooling system, said return chamber inlet opening into the return chamber of the vessel and also receiving a second end portion of the shaft that penetrates through the second end of the vessel, thereby externally supporting said second end portion of the shaft outside the vessel;   a supply chamber outlet on the circumferential wall at a location situated axially near the first end to enable supply of the working fluid from the supply chamber into the secondary loop; and   a return chamber outlet on the circumferential wall at a location situated axially near the second end to enable output of the working fluid from the return chamber into the primary loop.