Hydraulic Separation Moving Beyond Priamry / Secondary Piping...

Transcription

1 Hydraulic Separation Moving Beyond Priamry / Secondary Piping... load! #1 load! #2 load! #3 primary! circulator presented by: John Siegenthaler, P.E. Appropriate Designs Holland Patent, NY parallel! primary! circuit crossover! bridge closely! spaced! tees balancing valves Copyright 2012, J. Siegenthaler, all rights reserved. The contents of this file shall not be copied or transmitted in any form without written permission of the author. All diagrams shown in this file on conceptual and not intended as fully detailed installation drawings. No warranty is made as the the suitability of any drawings or data for a particular application.

2 Hydraulic Separation It s not just about hydraulic separators... Today s topics... What is common piping? Whatʼs the relationship b/w common piping & hydraulic separation? It doesnʼt have to be perfect What is the ideal hydronic header? Achieving hydraulic separation using low resistance heat souce Achieving hydraulic separation using closely spaced tees Achieving hydraulic separation using a buffer tank Achieving hydraulic separation using a hydraulic separator Divide & Conquer Examples of systems using hydraulic separation

3 What is COMMON PIPING? Itʼs the piping components shared by two or more circuits. common piping circulator 2 circuit 2 circuit 1 circulator 1 The degree to which two or more operating circulators interact with each other depends on the head loss of the common piping. The lower the head loss of the common piping the less the circulators will interfere with each other. When the head loss of the common piping is very low, there is hydraulic separation between the circuits.

4 When the head loss of the common piping is very low, there is hydraulic separation between the circuits. Very little head loss occurs! in this portion of the circuits. circulator 2 circuit 2 circuit 1 circulator 1 common piping

5 Very little head loss occurs! in this portion of the circuits. circulator 2 circuit 2 circuit 1 head loss curve including! common piping (both circulators on) circulator 1 common piping circuit 1 Assume that circulator 1 is operating, but that circulator 2 is off. The lower (blue) system head loss curve in figure 2 applies to this situation. Next, assume circulator 2 is turned on, and circulator 1 continues to operate. The flow rate through the common piping increases, and so does the head loss across it. However, because of its spacious geometry, the increase in head loss across the common piping will be very slight. The system head loss curve that is now seen by circulator 1 has very slightly steepened. It is the upper, (green) curve shown in figure 2. head loss (feet of head) 0 0 circuit 1 head loss curve including! common piping (1 circulator on) pump curve! (circulator 1) flow rate VERY small decrease in! circuit 1 flow rate! when circuit 2 is on very small change in! head loss across! common piping! when both circuits are on The operating point of circuit 1 has moved very slightly to the left, and as a result, the flow rate through circuit 1 has decreased very slightly. flow rate in circuit 1 when BOTH circuits! are operating flow rate in circuit 1 when it is the only circuit operating

6 Almost Perfect Is Good Enough: Very little head loss occurs! in this portion of the circuits. circulator 2 circuit 2 circuit 1 circulator 1 common piping Imagine a hypothetical situation in which the head loss across the common piping was zero, even with both circuits operating. Because NO head loss occurs across the common piping, it would be impossible for either circulator to influence the other circulator. This would be perfect hydraulic separation. Fortunately, perfect hydraulic separation is not required to ensure that the flow rates through independently operated circuits remain reasonably stable.

7 Common piping with high flow resistance is NOT good: common piping (with HIGH FLOW RESISTANCE) circulator 2 circuit 2 circuit 1 circulator 1 The higher the flow resistance of the common piping, the more each circulator will influence flow in the other circuit (e.g. the lower the hydraulic separation of the circuits.

8 High flow resistance common piping - something to avoid D 144!P = ( Head ) % ' & " $ # head added (feet) psi P at 0 flow pump curve! for small circulator flow rate (gpm) small circulator P=22 psi large circulator P=17psi backseated! flow check P= 10 psi ON ON P produced" by 0 flow = 4 psi P = 5 psi ON larger circulator ON smaller circulator P=12 psi P= 5 psi P=13 psi P=16 psi P=17 psi no flow common piping and! heat source have! HIGH FLOW RESISTANCE common piping and! heat source have! high flow resistance

9 Multi-zone system - using zone circulators other zone circuits OK zone circulators with spring-loaded check valves compact mod/con boiler purging! valves low flow resistance headers other zone circuits high flow resistance of compact boiler creates flow bottleneck zone circulators with spring-loaded check valves purging! valves NOT OK low flow resistance heat source Always keep the flow resistance of the common piping as low as possible. This provides hydraulic separation between circulators. Always provide a check valve on each zone circuit.

10 Divide & Conquer: Hydraulic separation allows designers to think of an overall system as a collection of independent ( hydraulically isolated) circuits. circulator 2 circuit 2 circulator 2 circuit 1 circuit 2 common! piping common! piping circulator 1 circuit 1 common! piping circulator 1 From the standpoint of hydraulics, each circuit can be designed as if itʼs a stand-along circuit. More on this later...

11 Primary / Secondary piping - where it all began... secondary circuit Primary / secondary piping, using closely spaced tees, is now well known and often used in North America. secondary! circuit load! #1 secondary! circuit load! #2 primary! circulator Primary / secondary piping, is one way to achieve hydraulic separation between circulators. But primary / secondary piping is not the ONLY way to create hydraulic separation... primary! circuit! (series) load! #3 secondary! circuit closely! spaced! tees! (typical)

12 Series and parallel primary/secondary systems secondary circuit SERIES primary loop secondary! circuit secondary! circuit PARALLEL primary loop load! #1 load! #2 load! #1 load! #2 load! #3 primary! circulator parallel! primary! circuit primary! circulator crossover! bridge primary! circuit! (series) closely! spaced! tees! (typical) closely! spaced! tees balancing valves load! #3 secondary! circuit Both series and parallel primary/secondary systems require a primary circulator. This adds to the installed cost of the system AND adds hundreds, even thousands of dollars in operating cost over a typical system life.

13 An example of primary loop circulator operating cost: Consider a system that supplies 500,000 Btu/hr at design load. Flow in the primary loop is 50 gpm with a corresponding head loss of 15 feet (6.35 psi pressure drop). Assume a wet rotor circulator with wire-to-water efficiency of 25 is used as the primary circulator. The input wattage to the circulator can be estimated as follows: W = f ΔP 0.25 = = 552watts Assuming this primary circulator runs for 3000 hours per year its first year operating cost would be: 1st year cost = 3000hr yr 552w 1kwhr whr $0.10 = $ kwhr

14 An example of primary loop circulator operating cost: Assuming electrical cost escalates at 4% per year the total operating cost over a 20-year design life is: c T = c 1 ( 1+ i ) N 1 i = $ ( ) 20 1 = $4,931 This, combined with eliminating the multi-hundred dollar installation cost of the primary circulator obviously results in significant savings.

15 Question: What is the ideal header in a hydronic system? Answer: One that splits up the flow without creating head loss Think about a copper basketball with pipes sticking out of it in all directions. very low head loss! inside header Wouldnʼt this be pretty close to an ideal header???

16 So why donʼt we build headers like this??? Instead, we approximate the ideal header by making it short & fat very low head loss! inside header Short / fat headers are GOOD! Long / skinny headers are BAD! short fat

17 So whatʼs EXACTLY is a short / fat header??? max (design) flow rate short select pipe size that yields a flow velocity no higher than 2 feet per second fat

18 Hydraulic separation achieved by low flow resistance heat source & short / fat headers. The low flow resistance heat source maintains low flow resistance of common piping very low flow resistance! common piping! low flow resistance heat! source size headers for max flow velocity of 2 ft/sec The short / fat headers hydraulically separate the distribution circulators from each other.

19 Hydraulic separation achieved by closely spaced tees & short / fat headers. high flow! resistance boiler The short / fat headers hydraulically separate the distribution circulators from each other. The closely spaced tees hydraulically separate the heat source from the header system. closely spaced tees size headers for max flow velocity of 2 ft/sec very low flow resistance! common piping!

20 Hydraulic separation achieved by closely spaced tees & short / fat headers. multiple! boiler! controller ouside! sensor The short & fat header and close spacing between supply and return connections results in a low pressure drop between points A and B. Each load circuit is hydraulically separated from the others. Header should be sized for max. flow velocity of 2 feet per second A closely! space! tees air! vent zone circulators! (w/ check valves) supply! temperature! sensor Each circuit must include a check valve. The supply temperature sensor must be downstream of the point of hydraulic separation. The header can be vertical (as shown) or horizontal. B drain! valve purge! valves "short/fat" header

21 Hydraulic separation achieved by buffer tank (piped as shown ) & short / fat headers. boiler! circulator The buffer tank hydraulically separate the heat source from the header system. high flow resistance boiler very low flow resistance! common piping! buffer! tank size headers for max flow velocity of 2 ft/sec The short / fat headers hydraulically separate the distribution circulators from each other.

22 VENT Hydraulic separation achieved by buffer tank to / from other heating zones wood gasification boiler ThermoCon tank

23 VENT Hydraulic separation achieved by buffer tank chilled water air handlers zoned chilled water cooling insulate all chilled water piping! to prevent condensation cooling mode reversing! valve temperature! sensor condenser evaporator chilled water ThermoCon tank purging! valves earth loop circuits Only tanks with sprayed foam insulation should be used for chilled water storage.

24 Hydraulic Separation in Micro-load systems: The small insulated tank provides: Thermal buffering Hydraulic separation Air separation and collection Sediment separation and collection outdoor! temperatue! sensor TRV thermostatic! radiator valves! (TRV) on each! radiator TRV TRV TRV TRV TRV variable speed! pressure-regulated! circulator manifold! station indirect water heater buffer tank, also serves as hydraulic separator,! air separator, dirt separator

25 Hydraulic separation achieved by hydraulic separator. The hydraulic separator hydraulically separates the heat source from the header system. high flow! resistance boiler The short / fat headers hydraulically separate the distribution circulators from each other. hydraulic separator size headers for max flow velocity of 2 ft/sec very low flow resistance! common piping!

26 Whatʼs going on inside a hydraulic separator? air vent area = A diameter = 1" air bubbles can rise faster than the downward water flow flow velocity = 4 ft/sec flow rate = 6.5 gpm flow velocity = 0.44 ft/sec flow rate = 6.5 gpm diameter = 3" area = 9A almost zero pressure drop b/w! upper and lower connections dirt particle drop into lower bowl drain valve The low vertical velocity inside the separator produces minimal pressure drop top to bottom. Thus there is very little tendency to induce flow on the load side of the separator.

27 What does the coalescing media do inside a hydraulic separator? air vent air vent upper coalescing media encourages! air bubbles to form "STANDARD"! hydraulic! separator HIGH PERFORMANCE! (air & dirt removal)! hydraulic separator air bubbles "ride" up the vertical filaments of the coalescing media - out of the active flow zone lower coalescing media encourages! dirt particle to drop! out of active flow zone drain valve drain valve The coalescing media creates tiny vortices that cause gas molecules (mostly oxygen and nitrogen) to form microbubbles. The media also helps microbubble merge together and rise upward out of the active flow zone.

28 Why companies that offer air and dirt separators also offer hydraulic separators... air vent air vent air vent air vent high performance! (microbubble)! air separator CUT WELD CUT WELD high performance! (low velocity zone)! dirt separator drain valve drain valve drain valve drain valve

29 High performance hydraulic separators provide three functions: 1. hydraulic separation 2. air separation 3. dirt separation Hydraulic! Separator boiler circuit distribution system heating! load(s) boiler circuit air! separator closely! spaced! tees distribution system heating! load(s) sediment! strainer

30 As the flow rates of the boiler circuit and distribution system change there are three possible scenarios: 1. Flow in the distribution system is equal to the flow in the boiler circuit. 2. Flow in the distribution system is greater than flow in the boiler circuit. 3. Flow in the distribution system is less than flow in the boiler circuit. Each case is governed by basic thermodynamic...

31 Case #1: Distribution flow equals boiler flow: T 1 f 1 f 2 T 2 NOTE: f 1 = f 3 (always!) NOTE: f 2 = f 4 (always!) f 3 f 4 T 3 T 4 In this case only:! T 1 = T 2 T 3 = T 4 Very little mixing occurs because the flows are balanced.

32 Case #2: Distribution flow is greater than boiler flow: T 1 f 1 f 2 T 2 The mixed temperature (T 2 ) supplied to the distribution system can be calculated with: NOTE: f 1 = f 3 (always!) NOTE: f 2 = f 4 (always!) T 2 = ( f 4 f 1 )T 4 + ( f 1 )T 1 f 4 T 3 f 3 f 4 T 4 Where: f4 = flow rate returning from distribution system (gpm) f1 = flow rate entering from boiler(s) (gpm) T4 = temperature of fluid returning from distribution system ( F) T1 = temperature of fluid entering from boiler ( F) Mixing occurs within the hydraulic separator.

33 Case #3: Distribution flow is less than boiler flow: Heat output is temporarily higher than current system load. Heat is being injected faster than the load is removing heat. T 1 f 1 f 2 NOTE: f 1 = f 3 (always!) NOTE: f 2 = f 4 (always!) T 2 The temperature returning to the boiler (T 3 ) can be calculated with: T 2 = ( f 4 f 1 )T 4 + ( f 1 )T 1 f 4 T 3 f 3 f 4 T 4 Where: T3 = temperature of fluid returned to boiler(s) ( F) f1 = flow rate entering from boiler(s) (gpm) f2, f4 = flow rate of distribution system (gpm) T1 = temperature of fluid entering from boiler ( F) T4 = temperature of fluid returning from distribution system ( F) Mixing occurs within the hydraulic separator.

34 Sizing of Hydraulic Separators: Hydraulic separators must be properly sized to provide proper hydraulic, air, and dirt separation. Excessively high flow rates will impede these functions. The size of a hydraulic separator refers to the nominal piping size of the 4 side connections (not the diameter of the vertical barrel). The piping connecting to the distribution side of the Hydro Separator should be sized for a flow of 4 feet per second or less under maximum flow rate conditions. union connections flange connections Pipe size of hydraulic separator Max flow rate (GPM)

35 Typical European concepts for multiple mod/con installation:

36 Typical European concepts for multiple mod/con installation:

37 Boiler manifold with integral hydraulic separator (courtesy Sinus North America). Form fitting insulation is supplied with all manifolds. Flexible piping connects each boiler to low manifold. (Boilers have integral circulators and check valves.) Notice that two additional boilers can be added to the front side of lower manifold.

38 Here's what the real products look like

39 How about 8 mod/cons with integral hydraulic separator (courtesy Sinus North America). Think of the output per unit of mechanical room floor area Each boiler can be independently serviced. Flexible piping connects each boiler to low manifold. (Boilers have integral circulators and check valves.)

40 Example of Hydro Separator Installation in New System: Magna Steel Corporation - Connecticut Photos courtesy of Peter Gasperini - Northeast Radiant

41 Example of Hydro Separator Installation in Old System: Because hydraulic separators remove sediment fromsystems they re ideal for applications where new boilers are retrofit to old distribution systems.

42 Example of Hydro Separator Installation in Old System: Because hydraulic separators remove sediment from systems theyʼre ideal for applications where new boilers are retrofit to old distribution systems. multiple! boiler! controller outdoor! temperature! sensor supply! temp.! sensor hydraulic! separator from existing system sediment capture! and removal

43 A hydraulic separator is a great way to interface a new mod/con boiler to a older steam conversion system. WHY? mod/con boiler! w/ compact heat exchanger existing cast-iron radiators (converted from steam) vent supply! temperature! sensor ECM! pressure! regulated! circulator hydraulic! separator existing piping Dirt separation is especially important in older systems with iron components.

44 Hydraulic Separators will likely become a key component in multiple ground source heat pump applications. The will allow the flow rate in the earth loop to be different than the flow rate through the heat pump array - more on this later... variable-speed! pressure-regulated! circulator to / from! other heat pumps zone! valve balancing! valve heating mode reversing! valve evaporator condenser water-to-water! heat pump geothermal manifolds hydro! separator purging! valves purge earth loop circuits fluid feeder

45 VENT Hydraulic Separators will likely become a key component in multiple ground source heat pump applications. circulator! w/ check circulator! w/ check circulator! w/ check heating mode heating mode heating mode compressor reversing! valve evaporator condenser TXV compressor reversing! valve evaporator condenser TXV compressor reversing! valve 3-way! diverter! valve AB AB AB A B A B A 12D 12D A AB B A AB B insulate all chilled water piping! to prevent condensation size all header piping for maximum flow velocity of 2 ft/sec to provide hydraulic separation insulate all chilled water piping! to prevent condensation chilled water air handlers evaporator condenser B 12D A AB B geothermal manifolds fixed speed! or! variable-speed! circulator TXV water-to-water! heat pump 3-way! diverter! valve temperature! sensor variable-speed! pressure-regulated! circulator to / from other heating zones hydro! separator purging! valves purge chilled water buffer tank earth loop circuits fluid feeder! (optional) temperature! sensor variable-speed! pressure-regulated! circulator warm water buffer tank

46 Divide & Conquer: Hydraulic separation allows designers to think of an overall system as a collection of independent ( hydraulically isolated) circuits. circulator 2 circuit 2 circulator 2 circuit 1 circuit 2 common! piping common! piping circulator 1 circuit 1 common! piping circulator 1 From the standpoint of hydraulics, each circuit can be designed as if itʼs a stand-along circuit.

47 Divide & Conquer: Simplifying system analysis Preventing flow interference

48 thermostatic radiator valves! Divide & Conquer: panel radiator TRV on each panel radiator TRV TRV TRV This portion of system filled with 40% solution of inhibited propylene glycol! brazed plate SS! heat exchanger TRV TRV manifold G! (garage) 3/4" copper P8 30 psi! PRV strap-on! aquastat! contacts! close at 100ºF! open at 50ºF HW P&TRV supply sensor 356 injection mixing controller fill/purge P7 variable speed! pressure regulated! circulator! set for Pc 12D to / from other! radiators These panel radiators are representative! of second floor heating distribution system! exact size and number of panels may vary,! but all are supplied with 1/2" PEX-AL-PEX tubing, and controlled by individual thermstatic radiator valves. CW 12D 1.25" copper tank 1.25" copper acqustat swing! check 12D PRV 2" air separator MRHL P1 LWCO 2" copper brass unions! (typical) 12D 3/4" copper P6 12D 1" copper 3/4" copper 3/4" fast fill piping 3/4" cold water supply 12- circuit manifold distribution system using PEX or PEX-AL-PEX tubing 2" copper balancing! valve balancing! valve! indirect water heater floor! drain cast-iron sectional boiler! with oil burner 12D 3/4" copper 12D In a complex system like this... return temperature! sensor for 356! mixing controllers 2" copper supply! and return headers! keep as short as possible all three injection pumps! equipped with internal! check valves 1" copper 1" copper 3/4" copper 1.25" copper 12D purging! valves P3 356 injection mixing controller closely spaced tees P2 outdoor! sensor 1" copper! mix supply! sensor 1" copper 3/4" copper 3/4" copper 3/4" copper 3/4" copper 3/4" copper 3/4" copper 1.25" copper 12D 1" copper Webstone! purging! valves 3/4" copper P5 closely spaced tees P4 outdoor! sensor 356 injection mixing controller variable speed! pressure regulated! circulator! set for Pc! mix supply! sensor 1" copper zone valves 3/4" copper 3/4" copper 3/4" copper 3/4" copper How does the water know where to go??? manifold A manifold B manifold C manifold D manifold E manifold F manifold H (2nd floor) manifold I (2nd floor)

49 TRV TRV Divide & Conquer: TRV TRV TRV TRV Hydraulic separation allows designers to think of an overall system as a collection of independent ( hydraulically isolated) circuits. cast-iron sectional boiler P1 P8 P7 low flow resistance heat source! + short / fat headers P3 P6 P5 P2 P4 In this system, hydraulic separation was achieved using short / fat header in combination with low flow resistance heat source. manifold H (2nd floor) manifold I (2nd floor)

50 VENT You find it: Where is the hydraulic separation in this system? chilled water air handlers DHW P&TRV electric! heating! element reversing! valve condenser evaporator insulate all chilled water piping! to prevent condensation heating is off to / from other heating zones water heater cooling mode temperature! chilled sensor water variable-speed! pressure-regulated! circulator TXV buffer tank geothermal manifolds purging! valves earth loop circuits

51 You find it: Where is the hydraulic separation in this system? indoor unit! outdoor unit OUTSIDE INSIDE make-up! water & supllemental! expansion tank thermostatic tempering valve motorized diverter valve indiret water heater with auxiliary electric element low flow resistance headers flow setter zone valve air handler w/ drip pan closely! spaced! tees variable speed! pressure regulated! circulators purge! valve low temperature space heating chilled water cooling

52 Hydraulic Separators now available in North America Caleffi Spirotherm Bell & Gossett Sinus North America Precision Hydronic Products Taco

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