Hydronic Equipment. Will Rea and Paul Pilutti June 16th, 2011

Transcription

1 Hydronic Equipment Will Rea and Paul Pilutti June 16th, 2011

2 Optimum Air Follow Up U of T Robarts Addition Under design Did energy modeling with reduced LAT Allowed for a 10-15% reduction in supply CFM Helped to deal with a mechanical space problem

3 Contents Fundamentals Pump Curves Heat Transfer Technology Pumps/HX/Accessories Applications Fire Pumps Parallel Pumping Case Studies Pressure Breaks Winter Free Cooling

4 Fundamentals

5 Motivation Why use Hydronics? Water is a more dense energy movement material than air Can move same energy in 4 pipe as 60 x60 duct Water experiences little heat gain in pipe Can be used in sub freezing temp with addition of glycol Evaporation produces adiabatic cooling on WB line

6 Pumps Nearly all HVAC pumps utilize centrifugal impellers Fluid drawn in through eye and discharged into volute Impeller can be trimmed to meet conditions High absolute velocity at impeller tip Discharge nozzle Volute efficiently decreases velocity Maintained relative velocity Suction eye

7 Hydronic Law Affinity Law Similar to First Fan Law (both uncompressed fluids) RPM to GPM to Head to BHP Big benefits in variable speed pumping (variable primary, etc.) Piping produces system curve just like ductwork Performance at intersection of impeller curve and system curve

8 Pump Curves Impeller Size Impeller Curves HEAD, ft. (m) " 13.0" 12.5" 12.0" 11.5" 11.0" 10.5" 70% 75% 78% 80% 82% 25HP 83% 83% 30HP 82% 80% System ½ Flow 6 x RPM System Curve CAPACITY, usgpm (l/sec) 40HP 50HP Efficiency Curves 78% 60HP 1800 BHP Lines Area of unknown

9 Pump Curves - VFD RPM Curves HEAD, ft. (m) RPM 1600 RPM 1450 RPM 1300 RPM 1150 RPM 1000 RPM 850 RPM Minimum ΔP 6 x RPM 70% 75% System Curve 78% 80% 82% 25HP 83% 83% 30HP CAPACITY, usgpm (l/sec) 82% 40HP 80% 50HP Efficiency Curves 78% 60HP BHP Lines Area of unknown 1800

10 Net Positive Suction Head When pumps suck up water a pressure loss occurs in the pipe If loss is too much, pressure drops and the water cavitates (boils) releasing steam bubbles Steam bubbles will cause extreme damage to impeller Typically only a problem in Open Systems Problem is very LOUD

11 Net Positive Suction Head - Calculation Available NPSH > Required NPSH or cavitiation occurs Cooling tower 10 above pump Pipe friction 15 Water at 85F NPSHR = 20 NPSHA>NPSHR Pump will function correctly

12 Net Positive Suction Head - Calculation Available NPSH > Required NPSH or cavitiation occurs Cooling tower 10 below pump Pipe friction 15 Water at 85F NPSHR = 20 NPSHA<NPSHR Pump will experience cavitation Move pump below tower basin

13 Heat Transfer Passive transfer from hot fluid to cold fluid Fluids can be water, steam, glycol, ethanol, air Overall rate q depends on resistance (U), area(a), temp difference(t) Temp difference is average approach or- Log Mean Temperature Difference

14 Counter vs. Parallel Flow All applications in HVAC are designed counter flow Counter flow allows temperature cross over greater heat transfer Increases LMTD less area required smaller HX No reason to ever do parallel flow

15 Fundamental Review Pump Curves Net Positive Suction Head Heat Transfer Counter vs. Parallel Flow

16 Technology

17 Pumps Used to move fluid and generate pressure Rated for flow (GPM) and head (resistance to flow) 3x4x6 - Inlet, outlet, max impeller Impellers can be trimmed in 1/8 increments Seals must be changed approx every 5 years HTS sells the ITT Brand largest manufacturer in the world

18 Impellers All centrifugal pumps use impellers to move fluids Curved vanes produce lift Single Suction Fluid is drawn through impeller eye on one side only Used on small pumps thrust load on impeller Double Suction Fluid drawn on both sides Balanced force on impeller, more efficient Vanes Straight good for high flow, low head (less drag) Curved good for high head, low flow (more lift)

19 Inline Advantages Typical for smaller pumps Pump motor mounted on top of volute Easy Install Disadvantages Weight rests on flanged connections Motor can become tuning fork Motor replacement can be challenging How to isolate correctly?

20 Base Mount Advantages Recommend for any large pump (25hp and above) Volute and motor mounted on a frame Removes strain on volute flanges Offers upblast (less footprint) Easier to Isolate Disadvantages More expensive than vertical in small sizes

21 Multi-Stage Each impeller can only handle so much head Very high lift (high rise buildings) need large lift for open systems Use multiple impellers in series to increase lift Each volute feeds suction of next impeller Have very low NSPHR Operate otherwise like a normal pump

22 Seals Pumps typically are open drive style Shaft must connect to volute casing through seal Seals typically can last up to 20,000 hrs. Gland Seal Made of Teflon/Graphite rings that sit around shaft Compressed into stuffing box by packing material Need to drip slightly to cool the seal No dripping will cause seal to overheat and fail Mechanical Seal Uses a compression ring to force to a stationary ring against rotating ring Located inside volute, water cooled No leakage no makeup water required reduces problems

23 Split Coupled vs. Close Coupled Pumps need seal changes Need access to seal Close Coupled Typical for smaller pumps (<7.5 HP) Motor must be removed to replace seal Split Coupled Split between motor and volute Motor can remain during seal replacement

24 Heat Exchangers Used to move thermal energy from fluid to fluid Used to break glycol/non-glycol systems Typically designed for equal flow on both sides Helps balance pressure drop and reynolds number

25 Shell and Tube Contains tubes within an exterior shell One fluid travels through tubes, other in shell Cross-over not possible Easy to clean tubes Tubes ridged to allow more surface area Very common in chillers Tube-in-tube similar, single internal tube HeadTube Bundle Shell

26 Plate and Frame Contains series of plates back to back Cross-over possible Clean in off season or with chemicals Can vary number of plates More plates = better approach Can add plates after unit is installed to change performance Can be built on site Bay st

27 Brazed Plate Contains series of plates back to back Plates are brazed together to form a complete unit Cross-over possible Chemical cleaning only Not as many options as Plate and Frame Can not add plates at a later date Low cost almost disposable

28 Air Separators Air is not good for hydronic systems Causes noise, restrictions, and damage Air seperator removes the air from water In open system with make up water, air constantly added

29 Expansion Tanks Water incompressible, expands with temperature Needs room or pipes break Gas used as buffer to expansion Diaphragm Tank Bladder Tank Diaphragm prevents mixing of fluids Bladder holds fluid Diaphragm limits acceptance Best design most acceptance volume Gas Water Water

30 Solids Separator Open Cooling tower are excellent are filtering contaminants out of air into water Also very good at adding air 2% make up water per hour adds contaminents Solids can very quickly build up Separators remove the solid from flow Do not experience filter build up Full presentation in April 2012

31 Accessories Triple Duty Valve Installed downstream of pump Check Valve Balancing Valve Service Valve Suction Diffuser Pump suction requires laminar flow Straight pipe for 5 pipe diameters or suction diffuser creates laminar flow Also contains strainer (need access to clean)

32 Technology Review Base vs. Inline pumps Shell, Plate Frame, Brazed Plate HX Air Seperators Expansion Tanks Lakos TDV/Suction Diffuser

33 Application

34 Fire Pump Packages Sprinkler systems typically run 0-1 times during a building life Need to always be under pressure Need to be able to instantly turn on to 100% flow Contain small pump and large pump Agency approved

35 Parallel Pump Packages Pumps pre mounted on skid, with controls and accessories Dual pump offer redudancy Pump selection more complicated Need system curve to cross single and double pump impeller curves Single pump Two pumps in operation Single pump does not cross system curve - BAD

36 System other than HVAC water Pool Water Chlorine damages copper use titanium/316 Stainless All plastic pumps Domestic Water Use brass fittings Glycol Make up and drains need to be carefully controlled Can not drain glycol to sewer

37 Application Review Fire pump packages Parallel Pumping Systems other than water

38 Case Studies

39 Floor Space Install Inline vs. Base Mount Advantages Typical for smaller pumps Pump motor mounted on top of volute Up blast allows correct straight pipe into suction

40 High-Rise Pressure Break Tall building create high pressures at lower levels Heat exchangers separate loops Loop temperatures rise with building Can keep pressure (and costs down)

41 Chiller Plant Free Cooling Optimal Conventional

42 Mt Sinai Hospital

43 Do NOT do HX in parallel flow poor heat transfer Run a pump dry will destroy the seal very quickly Selected parallel pump that does not cross both impeller curves

44 Questions? Questions?