Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
  • F28F9/00—Casings; Header boxes; Auxiliary supports for elements; Auxiliary members within casings
  • F28F9/26—Arrangements for connecting different sections of heat-exchange elements, e.g. of radiators
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
  • F28F27/00—Control arrangements or safety devices specially adapted for heat-exchange or heat-transfer apparatus
  • F28F27/02—Control arrangements or safety devices specially adapted for heat-exchange or heat-transfer apparatus for controlling the distribution of heat-exchange media between different channels
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F24—HEATING; RANGES; VENTILATING
  • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
  • F24F11/00—Control or safety arrangements
  • F24F11/70—Control systems characterised by their outputs; Constructional details thereof
  • F24F11/80—Control systems characterised by their outputs; Constructional details thereof for controlling the temperature of the supplied air
  • F24F11/83—Control systems characterised by their outputs; Constructional details thereof for controlling the temperature of the supplied air by controlling the supply of heat-exchange fluids to heat-exchangers
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F24—HEATING; RANGES; VENTILATING
  • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
  • F24F11/00—Control or safety arrangements
  • F24F11/70—Control systems characterised by their outputs; Constructional details thereof
  • F24F11/80—Control systems characterised by their outputs; Constructional details thereof for controlling the temperature of the supplied air
  • F24F11/83—Control systems characterised by their outputs; Constructional details thereof for controlling the temperature of the supplied air by controlling the supply of heat-exchange fluids to heat-exchangers
  • F24F11/84—Control systems characterised by their outputs; Constructional details thereof for controlling the temperature of the supplied air by controlling the supply of heat-exchange fluids to heat-exchangers using valves
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F24—HEATING; RANGES; VENTILATING
  • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
  • F24F11/00—Control or safety arrangements
  • F24F11/70—Control systems characterised by their outputs; Constructional details thereof
  • F24F11/80—Control systems characterised by their outputs; Constructional details thereof for controlling the temperature of the supplied air
  • F24F11/83—Control systems characterised by their outputs; Constructional details thereof for controlling the temperature of the supplied air by controlling the supply of heat-exchange fluids to heat-exchangers
  • F24F11/85—Control systems characterised by their outputs; Constructional details thereof for controlling the temperature of the supplied air by controlling the supply of heat-exchange fluids to heat-exchangers using variable-flow pumps
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
  • F28D1/00—Heat-exchange apparatus having stationary conduit assemblies for one heat-exchange medium only, the media being in contact with different sides of the conduit wall, in which the other heat-exchange medium is a large body of fluid, e.g. domestic or motor car radiators
  • F28D1/02—Heat-exchange apparatus having stationary conduit assemblies for one heat-exchange medium only, the media being in contact with different sides of the conduit wall, in which the other heat-exchange medium is a large body of fluid, e.g. domestic or motor car radiators with heat-exchange conduits immersed in the body of fluid
  • F28D1/04—Heat-exchange apparatus having stationary conduit assemblies for one heat-exchange medium only, the media being in contact with different sides of the conduit wall, in which the other heat-exchange medium is a large body of fluid, e.g. domestic or motor car radiators with heat-exchange conduits immersed in the body of fluid with tubular conduits
  • F28D1/053—Heat-exchange apparatus having stationary conduit assemblies for one heat-exchange medium only, the media being in contact with different sides of the conduit wall, in which the other heat-exchange medium is a large body of fluid, e.g. domestic or motor car radiators with heat-exchange conduits immersed in the body of fluid with tubular conduits the conduits being straight
  • F28D1/05316—Assemblies of conduits connected to common headers, e.g. core type radiators
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
  • F28F27/00—Control arrangements or safety devices specially adapted for heat-exchange or heat-transfer apparatus

Definitions

• This invention relates to improvements in control of part load capacity of a fluid heat exchange device, especially a chilled water cooling coil used in air handling equipment and fan coil units for comfort cooling and industrial application.
• a fluid heat exchange device especially a chilled water cooling coil used in air handling equipment and fan coil units for comfort cooling and industrial application.
• the device is described for cooling application, but is usable for heating application as well.
• Preferred objects of the present invention include:
• the principle of this invention is circuit by circuit control of fluid flow. At full load all the circuits are active, thus there is fluid flowing through all the available circuits of the coil. At part load the flow of fluid is cut off to some of the circuits, while flow is maintained at or near full velocity in the active circuits . The number of active circuits at any given time is determined by the prevailing air side load on the coil. The effective coil surface temperature around the active circuits remains constant, so dehumidification is maintained at part load, while around the inactive circuits no heat exchange to the air takes place.
• the present invention resides in a control method for chilled water cooling coils and hot water heating coils used in comfort and industrial air conditioning applications, including:
• a movable piston located in the supply header of the coil. At full load the piston is at it's upper most position and all the circuits are active, thus receiving full flow of chilled water. The position of this piston is dictated by the prevailing sensible heat load on the coil. At partial load the piston is moved down, cutting off chilled water supply to the circuits above it's location.
• the percent of active circuits being proportional to the sensible load and the effective coil surface temperature around the active circuits remaining constant ensures that the latent capacity of the coil is also proportional to the sensible load.
• any sensible heat source be it up or down stream of the cooling coil is an effective source to enhance dehumidification of the conditioned space. This includes heat generated by light fittings in open return air plenums .
• the coil water side pressure drop at full load may be selected at a low value, as at part load there is no substantial change in fluid flow velocity in the active circuits and the movable piston presents only minimal resistance.
• the piston in the supply pipe header controls sensible capacity by cutting fluid flow to upper circuits and the piston in the return pipe header, near independently, controls latent capacity by cutting off fluid flow to the lower most circuits.
• the same air handling unit may be used to effectively treat humid outside air as well as serve the conditioned space.
• the natural limit to this application is having sufficient sensible heat to perform the necessary dehumidification. Should there be insufficient sensible heat, some kind of reheat needs to be applied, just as it would in case of a conventional air handling unit dedicated to treat outside air only.
• One particular embodiment of this invention employs a weighted piston in the supply pipe header.
• the weight of the piston is such as to impose the desired differential pressure across the coil thus ensure constant flow velocity in the active circuits.
• the weighted piston is acting as a pressure relief device, on rising pressure it moves up to expose more circuit entries, thus relieve the pressure and visa versa should the differential pressure across the coil fall.
• the flow velocity in the active circuits being constant at a fixed differential pressure across the coil, the number of active circuits thus the position of the piston is directly proportional to the water quantity flowing through the coil.
• monitoring the position of this weighted piston gives an accurate, repeatable option to monitor the fluid flow quantity. Addition of entering and leaving water temperature sensors provides energy monitoring capability.
• An optional interlock between the weighted free floating piston and external control valve will add self balancing capability. It is a limiting type interlock, when the free floating piston in the supply pipe header reaches it's upper most position, the external control valve is prevented from opening up further. Should the external control valve be wide open at start up, the same interlock commands the valve to close until the piston drops just below it's uppermost position, thus restricting the coil to design chilled water quantity. During normal operation the external control valve is driven by the sensible load on the coil, however when the design water flow is exceeded the limiting function takes preference. This self balancing ability is suitable for chilled and hot water distribution systems where the pressure change from full to minimum system load is relatively small. For distribution systems where large pressure variations are expected, it is preferred to include manual balancing valves .
• the design can incorporate low pressure drop coils and control valves, resulting in substantial pumping power reduction.
• pumping power reduction is proportional to the pressure head reduction due to the removal of the original high pressure drop control valve .
• a coil suitably sized to meet full load will perform and remain controllable at low partial loads .
• FIG. 1 is a schematic view of the first embodiment highlighting the principle of this invention, operating as a chilled water cooling coil.
• FIG. 2 shows the application of this coil in an air handling unit for treating high humidity outside air and also serving a conditioned space.
• FIG. 3 is a constant differential pressure, thus constant circuit flow velocity embodiment of this invention, with weighted free floating piston in the supply pipe header of the coil .
• FIG. 4 an alternative method to detect location of weighted free floating piston to facilitate water flow measurement.
• FIG. 5 is a simplified way to detect upper most position of weighted free floating piston for water side balance indication and self balancing.
• FIG. 6 shows an integral system powered control valve as an alternative to external control valve.
• FIG. 7 illustrates a system powered method of controlling pressure differential across the coil to facilitate latent / sensible capacity ratio control.
• FIG. 8 is a system pressure dependent low cost system powered alternative for general comfort cooling application.
• FIG 9 shows a system pressure dependent motorised positioning of control piston in supply header.
• Optional latent / sensible capacity ratio control by additional piston placed in return pipe header is also illustrated.
• FIG. 10 is a system powered alternative of positioning of control piston in return pipe header to facilitate latent / sensible capacity ratio control.
• FIG. 11 illustrates a three stage solenoid valve controlled approach, where a number of circuits are controlled as a group .
• FIG. 12 details of hydraulic actuated self propelled control piston.
• FIG. 13 associated control elements of hydraulic actuated self propelled control piston.
• FIG. 14 hybrid, hydraulic system and electric powered self propelled piston for pipe headers made of ferrous material .
• FIG. 15 as in FIG. 14 but suitable for ferrous and non ferrous coil pipe headers.
• FIG. 16 basic hydraulic actuated diaphragm circuit by circuit control without 100% positive shut off capability.
• FIG. 17 hydraulic actuated diaphragm with near independent latent and sensible capacity control, also 100% shut off capability.
• FIG. 18 basic system powered diaphragm control, no 100% shut off.
• FIG. 19 system powered diaphragm control with modified pipe connection to supply pipe header. 100% shut off capability.
• FIG. 20 hydraulic actuated diaphragm and external control valve, near independent sensible and latent control ability.
• FIG. 21 hydraulic actuated diaphragms for circuit by circuit control and integral throttle valve, near independent sensible and latent control.
• FIG. 22 mechanical actuated ball driven positioning of control piston with 100% shut off capability.
• FIG. 23 hydraulic actuated ball driven positioning of control piston with 100% shut off capability.
• FIG. 24 method of temperature based control piston position sensing.
• FIG. 25 pneumatic powered diaphragm control with sliding bottom end clip used on diaphragm, shown under part load condition.
• FIG. 26 same as in FIG. 25, however illustrated in the 100% shut off position.
• FIG. 27 hydraulic actuated diaphragm with external, non system, hydraulic source. Utilising hydraulic fluid of less than 1 specific gravity.
• FIG. 28 high pumping efficiency, low running cost, configuration with dedicated speed controlled pump.
• FIG. 29 using a slotted cylinder to control coils with relatively low number of circuits, such as used in fan coil units .
• the chilled water coil 1 has a supply header 2, return header 3, and interconnecting circuits 4, between supply end return pipe headers.
• the plurality of interconnecting circuits 4 are connected to each header 2, 3 by a corresponding plurality of connectinc ports 202 at different locations lying in a row one above the other along the header 2, 3. Fluid flow is supplied to the supply header 2 through supply port 201 at the bottom end of header 2 and is supplied from return header 3 through return port 203 at the top end of return header 3.
• piston 5 cuts off the water flow to the upper three circuits 6, the coil surface temperature in the region of circuits 6, is the same as of the entering air and no heat exchange takes place.
• the circuits 4, below the lower edge of piston 5, are active, receiving full supply of chilled water and the coil surface temperature around circuits 4, is at design temperature. Air traversing this region is cooled and dehumidified.
• Moving piston 5, upwards increases both sensible and latent capacities of the coil. Moving piston 5, downwards reduces both sensible and latent capacities .
• the ratio of sensible versus latent capacity is defined at the coil selection / design stage and this ratio remains constant at partial load across the whole operating range.
• piston 5 The position of piston 5, is determined by the prevailing sensible load as sensed by a space or return air dry bulb temperature sensor. For most comfort cooling applications sensible heat control is sufficient and piston 5, is the only required control element.
• piston 7, located in the return pipe header.
• piston 7, is at it's lower most position. Elevating piston 7, thus cutting off water flow through the lowest circuits 8, results in a reduction of latent capacity.
• the condensate forming on the cold surface in the region of active circuits 4, reaching coil surface around inactive circuits 8, is partly or fully evaporated, thus reducing latent capacity and increasing the sensible by evaporative cooling the air passing through the lower portion of the coil. Should it be desired, by sufficiently elevating piston 7, in return header 3, a position is reached where the cooling coil is doing pure sensible cooling without effecting the total moisture content of the air stream.
• cooling coil 1 In this illustration only the lower, shaded half of cooling coil 1, is active.
• Return air enters at location 12 outside / fresh air enters at 13, and the supply air leaves the air handling unit at location 14.
• External control valve 16 is of low pressure drop type when in the full open position, as for example a butterfly valve.
• the degree of opening of this motorised valve is determined by space or return air temperature deviation from setpoint, thus by the prevailing sensible load on the coil.
• the weight of piston 5, is chosen to equal the design pressure difference between supply header 2, and return header 3. For this free floating piston 5, to remain stationary, the supply header pressure acting on it's bottom must equal the return header pressure acting on it's top plus the weight of the piston.
• This pressure drop change at valve 16, shows up as a pressure differential increase across the coil, piston 5, is no longer in balance at it's current position and starts to ride up, permitting water to flow through more circuits, thus reducing the differential pressure across the supply and return pipe headers.
• the constant differential pressure maintained by piston 5, ensures constant velocity in the active circuits and the number of active circuits is dependent on the position of this piston, knowing the position of piston 5, provides an accurate means of measuring the quantity of water flowing through the coil.
• an ultrasonic transducer / receiver 17 is placed at the upper end of supply header 2. With it's associated electronic circuitry the ultrasonic transducer / receiver operates as an echo sounder and measures the distance of piston 5, relative to the piston's upper most position. The coil manufacturer's data can accurately relate the position of piston 5, to water flow rate. The addition of entering and leaving water temperature sensors will provide the necessary inputs to compute the energy used by the coil. Temperature sensors are not illustrated in FIG 3. Mechanical stop 18, is to prevent piston 5, from going all the way to the bottom of supply header 2 and cutting off the entering water supply connection.
• Multi turn potentiometer 19 is direct coupled to threaded rod 21, which in turn supported by bearings 20, and 22.
• Bearing 20, also contains a water tight seal.
• Threaded rod 21, passing through piston 5, is meshed with female thread contained within piston 5, thus any up or down displacement of piston 5, from it's position causes threaded rod 21, to rotate.
• This in turn rotates potentiometer 19, and a change in resistance indicates the location of piston 5.
• the pitch of the thread on threaded rod 21, is high, in the order of a few turns representing the full travel of piston 5.
• piston 5 contains a permanent magnet 23.
• Magnetic reed switches 24, and 25, are located on the outside of and near the top of supply pipe header 2.
• both reed switches are in the off / normally open position.
• piston 5, moves up and permanent magnet 23, is in line with reed switch 24, it closes and indicates full water flow at correct differential pressure and velocity across the coil.
• magnetic reed switch closes it prevents control valve 16, from opening further.
• FIG. 6 where an integrated system powered control valve is shown as an alternative to external control valve 16, of FIG. 3, and 4.
• This system powered valve consists of piston 26, cylindrical protrusion 27, and valve seat 28, housed in the upper enlarged portion of return pipe header 3.
• Small diameter pipe 29, originates in entering water supply pipe and via filter 30, and solenoid valve 31, can supply high pressure water to space above piston 26.
• the water pressure available via solenoid valve 31, is greater than the pressure in return header 3, thus piston 26, is forced downwards, restricting the water flow rate and ultimately shutting it off when the lower lip of protrusion 27, is in contact with valve seat 28.
• solenoid valve 33 is opened, relieving the pressure above piston 26, and discharging the excess water via pipe 34, into the return water pipe.
• piston 26 When solenoid valves 31, and 33, are closed piston 26, maintains it's position. Pulsed opening of solenoid valves 31, and 33, moves piston 26, to the desired position, thus sets the required water flow rate.
• Protrusion 27, may be shaped other than cylindrical to facilitate linear valve characteristics. In normal operation position of piston 26, is set by the prevailing sensible load, derived from temperature deviation of space or return air from setpoint for constant volume air handlers . For variable volume air handlers the supply air temperature deviation from setpoint is the driver. If equipped with some form of position indication of weighted free floating piston 5, flow monitoring and water side system balance are handled as described in conjunction with FIG. 3, 4, and 5.
• piston 5 does not contain a weight.
• Vertical supply pipe header 2 is extended via a 90 degree bend into a horizontal section 42.
• Piston 43 is in this horizontal portion 42, of supply pipe header.
• Loose fitting balls 44, between piston 5, and piston 43 act as flexible "push rod” and transfer force between the two pistons.
• High pressure system water enters lower chamber of cylinder 36, via pipe 29, filter 30, fixed orifice 38, and pipe 39.
• the upper chamber of cylinder 36 is connected to the return pipe header 3, via pipe 40.
• solenoid valve 31 opens, admitting more water into chamber on right side of piston 43, which in turn forces piston 5, downwards via ball shaped spacers 44, cutting off water flow in some more circuits. Keeping solenoid valve 31, open after all the circuits are cut off, when lower surface of piston 5, reaches valve seat 45, all water flow through the coil is stopped. This would be the case when this particular air handling unit is not in service. Should the sensible load increase, solenoid valve 33, is opened permitting water to flow out from header 42, on right side of piston 43.
• solenoid valve 33 When the coil cooling capacity is matching the air side cooling load, solenoid valve 33, is closed. Valves 31, and 33, remain in the closed position, the number of active circuits remain the same, until there is a change in the air side load. For constant volume air handlers solenoid valves 31, and 33, are controlled by deviation from space or return air temperature setpoint, for variable volume air handlers by deviation from supply air temperature setpoint .
• Geared motor 45 drives worm screw 21, and piston 5, is coupled to worm screw 21, by a matching female thread.
• geared motor 45 turns worm screw 21, in one direction, piston 5, is moved upwards, reverse rotation causes piston 5, to move downwards.
• piston 5, is driven all the way down and it's lower surface contacts valve seat 46, all water flow through the coil is stopped.
• the vertical protrusion and groove in piston 5, are not illustrated.
• Bearings 20, and 22, are to maintain axial and radial positions of worm screw 21, and bearing 20, also contains a water tight seal.
• Geared motor 45 is under the control of prevailing sensible air side load.
• the optional latent / sensible capacity ratio control is accomplished by piston 7.
• the mechanism to position piston 7, in return header 3, is identical to the one described above in conjunction with piston 5.
• Geared motor 47, positioning piston 7, is under the command of space or return air relative humidity deviation from setpoint. Referring to FIG. 10, where a system powered version of positioning piston 7, in return header 3, is illustrated. System water may enter or escape from flexible bellows 48, via small diameter pipe 32, and bellows 48, in turn moves piston 7, to the desired position. Control piping arrangement, filter and solenoid valves are the same as illustrated in FIG. 8.
• the positioning signal for piston 7, originates from relative humidity deviation from setpoint.
• FIG. 11 illustrating three stage control of cooling coil by solenoid valves.
• Dividing plates 49 placed in supply pipe header 2 , create three separate chambers in supply header 2.
• the water flow to each chamber is controlled by individual solenoid valves 50, 51, and 52.
• valves 50, and 52 are closed and 51, is open, thus only circuits 4, are active and there is no water flow in circuits 6, and 8.
• the current operation mode is at reduced sensible capacity also at reduced latent / sensible capacity ratio.
• solenoid valves motorised on / off valves or modulating control valves may be utilised and the groups of circuits and valves are not limited to three.
• a self propelled hydraulic powered piston assembly is illustrated.
• This piston assembly is placed in the supply pipe header 2, of the cooling / heating coil.
• the three chambers 53, 54, and 55 may be pressurised via connecting pipes 56, 57, 58, respectively. Applying pressure to chamber 53, via pipe 56, expands flexible bellows 59, forcing split friction ring 60 , against the inner wall of pipe header 2, thus clamping the upper part of the piston assembly in place. Pressurising chamber 54, via pipe 57, will clamp the lower part of this piston assembly in position. Delivering pressurised fluid to chamber 55, via pipe 58, moves the upper and lower portions apart, as in illustrations A, & C.
• Permitting fluid to flow out from chamber 55 lets the upper and lower portions to move to close proximity as in illustration B. If chamber 53, is pressurised and chamber 54, is not under pressure, the lower portion of the piston assembly will move down when fluid is delivered to chamber 55, and move up when fluid is permitted to flow out from chamber 55. The upper part of the assembly may move up or down when the lower part is clamped in place in a similar manner. Thus alternate application of fluid pressure to chambers 53, 54, and 55, enables the piston assembly to "climb" up or down in pipe header 2.
• the pressurised fluid is derived from the system, flows through replaceable filter 30, fixed orifices 61, flexible pipes 56, 57, 58, to chambers 53, 54, and 55.
• the three chambers 53, 54, and 55 are pressurised. Opening one or more of the solenoid valves relieves the pressure in the respective chamber / chambers.
• An electronic controller not illustrated, generates the sequential signal to drive the piston assembly up or down according to the prevailing load on the coil.
• a dedicated hydraulic or pneumatic pressure source may be used.
• Another alternative is to incorporate solenoid valves 62, in the piston assembly and bring the connecting wires out from header 2 , in place of flexible hydraulic pipes 56, 57, 58.
• a magnetic clamping arrangement is shown suitable for non ferrous also for ferrous pipe headers.
• Split ring 65 of plastic and ferrite mix is loaded by springs 66, to expand and clamp against pipe header 2.
• solenoid 63 is energised to enable free movement of piston assembly portion within the pipe header. Closed and open positions of solenoid valve illustrated in A & B .
• a long tubular flexible diaphragm 67 is fitted inside pipe header 2.
• the upper expanded circular end of diaphragm 67 is connected to pipe 71, and the lower collapsed semi circular end is fastened to pipe header 2, at location 70.
• System fluid via filter 30, forced by pump 68, via non return valve 69, and connecting pipe 71, into below 67, extends the circular portion of diaphragm 67, downwards, closing off additional circuits.
• pump 68, off and opening solenoid valve 62 fluid is permitted to flow out from diaphragm 67, collapsing more of the circular section into semi circular and permitting water flow through more circuits of the coil .
• Illustrations A. & B. show expanded circular and collapsed semi circular sections of diaphragm 67, respectively. This particular configuration is suitable for cooling coils in humid tropical climate, where there is always some sensible and latent load on the coil and positive shut off of the water flow is not critical.
• tubular diaphragm 67 is turned 90 deg. clockwise, looking down supply header 2, end extended all the way to the bottom of same. Entering pipe connection 78, to supply header 2, is turned 90 deg. anti - clockwise and split into two connections to header 2. In this configuration full shut off of the chilled water flow through the coil is possible, besides circuit by circuit control of sensible coil capacity.
• the pressure inside tubular diaphragm 67 is maintained at a constant differential above the pressure in return pipe header 3.
• Control fluid pump 68 takes system fluid via filter 30, and delivers this fluid to diaphragm 67, via fixed orifice 61.
• Pressure relief valve 36 maintains this pressure at a constant level relative to the pressure in return header 3.
• the pressure differential maintained is equal to the design pressure drop of the coil.
• the action of diaphragm 67, in this application is same as of free sliding piston 5, described in association with FIG. 3.
• Butterfly valve 16 sets the quantity of chilled water flowing through the coil and controlled by the sensible load and diaphragm 67, maintains constant differential pressure across the coil by exposing more or less circuits to chilled water flow.
• Piston 35, of pressure relief valve 36 is made of ferrous material. Increasing / decreasing current flow through solenoid 37, the differential pressure setting of relief valve 36, is changed. The differential pressure maintained across the coil sets the sensible to latent capacity ratio of the coil, thus it is under relative humidity control.
• permanent magnet 23 comes to close proximity to reed switch 24.
• Contact closure of reed switch 24 indicates design flowrate across the coil when operating at design pressure drop. This may be used as an indication to facilitate water side system balancing or used as an interlock to prevent butterfly valve to open more, thus limiting the coil to it's design water quantity.
• diaphragm 67 the function and operation of diaphragm 67, is the same as described in conjunction with FIG. 20. The difference is in replacing the butterfly valve with diaphragm 75, and modification of return pipe connection 79. Solenoid valves 72, and 62, when open, will permit fluid flow to or from diaphragm 75, respectively. The solenoid valves are under sensible load control and diaphragm 75, is acting as a conventional throttle valve.
• free sliding piston 80 of positive buoyancy is located in supply pipe header 2.
• Rotating toothed wheel 81 clockwise transfers balls 82, from reservoir 83, to pipe header 2.
• the balls 82 force piston 80, downwards. Since piston 80, has a bore through it the pressure above and below the piston are the same, thus only a little force is required to overcome the the buoyancy of piston 80.
• the balls 82 are of slight positive buoyancy and if any circuit entrance above piston 80, is open to water flow, this flow tends to move the nearest ball to block the open circuit entry.
• Rotating toothed wheel 81, anti - clockwise transfers balls 82, from supply header 2, to reservoir 83, piston 80, now free to move up and more circuits become open to water flow. Toothed wheel 80, is driven by a gear motor, which is not illustrated, and is under the control of prevailing sensible load.
• moving balls 82, from reservoir 83, to supply pipe header 2 is accomplished by pump 68, supplying pressurised fluid via non return valve 69, to the space in reservoir 83, below piston 84. Opening solenoid valve 62, relieves the pressure under piston 84, in reservoir 83, and permits the balls 82, to move from header 2, to reservoir 83.
• Air handling unit 9 consisting of filter 10, cooling coil 1, and supply air fan 11. Return air enters the air handler 9, at location 12, and supply air leaves at location 14.
• Temperature sensor Tl is placed near the top of cooling coil 1, and temp, sensor T2 , is near the bottom of same. There is also a temp, sensor T3 , located in the leaving air stream. Where temperature sensed by T3 , falls between temperatures sensed by Tl, and T2, is proportional to % of coil circuits in operation, except when 100% or 0% of the circuits are active. At full and zero load all three temperatures sensed Tl, T2 , and T3 , are the same, however the full or zero load condition is easily determined from the actual value of sensed temperatures .
• a long tubular elastic diaphragm 67 is fitted inside pipe header 2.
• the upper expanded circular end of diaphragm 67 is connected to pipe 71, and the lower collapsed semi circular end is fastened to and sealed at sliding guide 70.
• Compressed air from air source 85 enters diaphragm 67, when solenoid valve 72, is open, via connecting pipe 71, extends the circular portion of diaphragm 67, downwards, closing off additional circuits.
• Solenoid valve 72, closed and solenoid valve 62 open air is permitted to exhaust out of diaphragm 67, collapsing more of the circular section into semi circular and permitting water flow through more circuits of the coil. Illustrations A. & B.
• a hydraulic fluid of lower than 1 in specific gravity is used to inflate the non uniform elasticity tubular diaphragm 67.
• the buoyant fluid is to ensure that the uppermost portion of diaphragm 67, takes up circular shape first, thus cuts off chilled water flow to the uppermost circuits first. When more hydraulic fluid is admitted, this circular shape extends downwards, cutting off water flow to more circuits progressively. Elevating the hydraulic fluid pressure inside diaphragm 67, above the prevailing pressure in supply pipe header 2, expands diaphragm 67, downwards and provides 100% water flow shut off.
• pump 68 To increase hydraulic fluid volume and or pressure in diaphragm 67, pump 68, is started and fluid is pumped from reservoir 86, via non return valve 69, and connecting pipe 71, into diaphragm 67. To reduce the fluid volume and or pressure in same, solenoid valve 62, is opened and the hydraulic fluid is free to flow back to reservoir 86.
• reservoir 86 may be directly pressurised from the chilled water supply pipe in order to minimise the load placed on pump 68.
• FIG. 28 where the same method of positioning of piston 5, in supply pipe header 2, is illustrated, as described in conjunction with FIG. 3, except that the butterfly valve is replaced with a variable speed pump 87.
• the pump speed is set by speed controller 88, which in turn is derived from space air temp, deviation from setpoint, thus from the prevailing sensible load on the coil.
• the weight of piston 5, is chosen to equal the design pressure difference between supply header 2, and return header 3. For this free floating piston 5, to remain stationary, the supply header pressure acting on it's bottom must equal the return header pressure acting on it's top plus the weight of the piston.
• Piston 5 is no longer in balance at it's current position and starts to ride up, permitting water to flow through more circuits, thus reducing the differential pressure across the supply and return pipe headers .
• the constant differential pressure maintained by piston 5, ensures constant velocity in the active circuits and the number of active circuits is dependent on the position of this piston, knowing the position of piston 5, provides an accurate means of measuring the quantity of water flowing through the coil.
• an ultrasonic transducer / receiver 17 is placed at the upper end of supply header 2. With it's associated electronic circuitry the ultrasonic transducer / receiver operates as an echo sounder and measures the distance of piston 5, relative to the piston's upper most position.
• the coil manufacturer's data can accurately relate the position of piston 5, to water flow rate.
• the addition of entering and leaving water temperature sensors will provide the necessary inputs to compute the energy used by the coil. Temperature sensors are not illustrated in FIG. 28.
• Mechanical stop 18, is to prevent piston 5, from going all the way to the bottom of supply header 2 and cutting off the entering water supply connection.
• a slotted cylinder 89 is placed inside supply pipe header 2.
• the slots 91, on cylinder 89, are progressively longer going from top towards the bottom. This is to ensure that the upper circuits are cut off from chilled water flow prior to progressing sequentially downwards.
• the opened up and flattened mantle 90, of control cylinder 89 also shows progression of length of slots 91.
• cylinder 89 is rotated through 180 degrees by modulating motor 92.
• Cylinder 89 is open at the bottom permitting supply chilled water to enter the cylinder. The supply water is admitted from inside cylinder 89, to coil circuits via slots 91.
• Circuit by circuit control shutting off the upper circuits first and progressing downwards provides sensible capacity control.
• Circuit by circuit control shutting off lower circuit first and progressing upwards facilitates latent / sensible load ratio control.
• Maintaining different water side differential pressure across the coil effects circuit flow velocity, thus temperature rise of chilled water consequently effective coil surface temperature, is another way of effecting latent / sensible load ratio control.
• At fixed differential pressure across the coil the water flow velocity in the circuits is constant, thus the number of active circuits is directly proportional to the water quantity through the coil, offering an accurate means for measuring water flow rate.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
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• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Magnetically Actuated Valves (AREA)
• Steam Or Hot-Water Central Heating Systems (AREA)
• Other Air-Conditioning Systems (AREA)
• Air Conditioning Control Device (AREA)
• Fluid-Pressure Circuits (AREA)

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• 2003
  • 2003-05-07 KR KR10-2004-7018066A patent/KR20040106511A/ko not_active Ceased
  • 2003-05-07 CN CNB038154374A patent/CN100371651C/zh not_active Expired - Lifetime
  • 2003-05-07 WO PCT/IB2003/001767 patent/WO2003095925A1/en not_active Ceased
  • 2003-05-07 EP EP03720783A patent/EP1504232A4/de not_active Withdrawn
  • 2003-05-07 US US10/513,976 patent/US20060191677A1/en not_active Abandoned
  • 2003-05-07 AU AU2003224357A patent/AU2003224357B8/en not_active Ceased
  • 2003-05-09 MY MYPI20031741A patent/MY135332A/en unknown
• 2007
  • 2007-07-11 US US11/776,182 patent/US20080000629A1/en not_active Abandoned

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