Course Title: Design Considerations For Hydronic Pump System
Fundamentals of Hydronic Design - Healthy Heating · Some slides contained animations in the...
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Fundamentals of Hydronic Design
Snow Melting
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Fundamentals of Hydronic Design Portions of this presentation are copy written by others, acknowledgments, credits
and references as noted.
Materials copy written © 2005, by the American Society of Heating, Refrigerating and AirConditioning Engineers, Inc. Reprinted with permission from ASHRAE
Applications Handbook. These materials can be purchased from the ASHRAE bookstore, www.ashrae.org
This material may not be copied nor distributed in either paper or digital form without permission. Some slides contained animations in the original .ppt format which have
been eliminated in the conversions to images or Adobe’s .pdf format.
If you wish to use this presentation for non commercial use, please contact [email protected] for details and restrictions.
This educational material was assembled and copy written © by Robert Bean, R.E.T., All Rights Reserved.
It is provided for “not for profit” educational purposes.
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Fundamentals of Hydronic Design
Courtesy of American Iron and Steel Institute
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Fundamentals of Hydronic Design
Seminar Objectives:
Design and Performance Considerations for Snow Melting Systems.
Boston Aerial Highway 1958 © The Aberdeen Group, All Rights Reserved
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Fundamentals of Hydronic Design
• Why Snowmelt? • Convenience, Safety and Security • Ensure access to buildings and services
• Piles of snow, snow drifts, ice etc. • Restricted access during removal by other means • Adds a dimension of “personal security” while at home or away.
• Eliminates other methods • Sand, salt, light or heavy gas powered snow removal equipment • Noise, fumes, safety of pedestrians including children and seniors.
• Reduces winter damage and spring clean up • Surfaces, stairs, landscaping, street cleaners etc.
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Fundamentals of Hydronic Design
Image Source: Development of a Two Dimensional Transient Model of SnowMelting Systems, and Use of the Model for Analysis of Design
Alternatives, ASHRAE 1090RP, 2001
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Fundamentals of Hydronic Design
• Surface Conditions • Dry • Wet • Dry Snow • Slush • Snow & Slush • Solid Ice • Solid Ice & Water Source: A Simulation Tool for the Hydronic Bridge Snow Melting System
Xiaobing Liu Jeffrey D. Spitler, Submitted to the 12th International Road Weather Conference, Oklahoma State University, School of Mechanical and Aerospace Engineering,
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Fundamentals of Hydronic Design
• Consider • Client • Control • Construct • Calculations
Courtesy of American Iron and Steel Institute
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Fundamentals of Hydronic Design
Client
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Fundamentals of Hydronic Design
Courtesy of American Iron and Steel Institute
• Client • Typical
• Residential • Commercial • Institutional • Industrial • Agricultural
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Fundamentals of Hydronic Design
• Client • Who is the client? • What are the expectations? • Where is it required? • When is it required? • Why is it required? • How Much?
• Capital, Operation, Maintain
The lowest cost snow melt system is available each year around spring time.
Words of Wisdom From John Barba
[;@)
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Fundamentals of Hydronic Design
• Client • Expectation
• Old Method • Class 1 • Class 2 • Class 3
• Current Method • Frequency Percentile
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Fundamentals of Hydronic Design
• Client • Frequency Percentiles • Percentage of time required snow melting load does not exceed the reported value. • 75, 90, 95, 98, 99 and 100 %.
• % of time Flux ≤ The Design for a Snow Free Area Ratio •Heliport vs. Residential Driveway • 100% @ Ar=1.0, 170˚F • 75% @ Ar=0.5, 140˚F
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Fundamentals of Hydronic Design Percentage of time required snow melting load does not exceed the reported value.
Ex. If the system was designed for 90% it means 10% of the time the load would be exceeded for that specific Area Ratio.
Source: Development Of Snow Melting Load Design Algorithms And Data For Locations Around The World, ASHRAE 926RP Final Report
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Fundamentals of Hydronic Design
• Client • Area Free Ratio • Ar = A f /A t , where •A f = equivalent snowfree area, ft 2
•A s = equivalent snowcovered area, ft 2
•A t = Af + As = total area, ft 2
• Ar = 1.0, No snow accumulation • Ar = 0.0, Complete coverage (no heat or evap. losses) • Ar = 0.5, slush (50% coverage)
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Fundamentals of Hydronic Design
• Client • Area Free Ratio • Expectation
• Influences • Temps • Spacing • Depth • Insulation • Striping • Bridging
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Fundamentals of Hydronic Design
Controls
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Fundamentals of Hydronic Design
Courtesy of American Iron and Steel Institute
• Controls • Response • Storm Characteristics
• Climate/Geography • Consumption
• Heat Release • Production
• Heat Generated
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Fundamentals of Hydronic Design Copyright © Building Science Corporation
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Fundamentals of Hydronic Design
Time
Copyright 2004, American Society of Heating, Refrigerating and Air Conditioning Engineers, Inc. and Oklahoma State University.
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Fundamentals of Hydronic Design
Time
Copyright 2004, American Society of Heating, Refrigerating and Air Conditioning Engineers, Inc. and Oklahoma State University.
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Fundamentals of Hydronic Design
Time
Copyright 2004, American Society of Heating, Refrigerating and Air Conditioning Engineers, Inc. and Oklahoma State University.
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Fundamentals of Hydronic Design
• Controls • Question Is… • How to Respond to Unknown Storm Characteristics • Think Performance & Operating Cost
• Manual – “Reactive” • On/off
• Automated – “Proactive” • On/Off • Idle/on/Idle
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Fundamentals of Hydronic Design
• Controls • On/off • “Heat fluxes up to five times greater than those indicated by steadystate analysis need to be delivered to the slab in order to keep its surface clear from snow during the early hours of the snowfall when the heating system is just starting to operate.” Source: Development of a Two Dimensional Transient Model of SnowMelting Systems, and Use of the Model for Analysis of Design Alternatives, ASHRAE 1090RP, 2001
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Fundamentals of Hydronic Design
• Controls • Idle/on • Reduce pick up loads • Increases “stand by” losses • Improves performance • Can be impractical for some applications
• Warm weather shut down • Cold weather shut down
“Without idling, very high fluxes are required to raise the slab temperature
sufficiently at the start of the storm.”
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Fundamentals of Hydronic Design
RPA Guidelines for the Design And Installation of Radiant Panel Heating and Snow/Ice Melt Systems (2004 Edition).
All Rights Reserved.
• Controls • Monitor
• Outdoor Temp • Precipitation • SIM Supply / Return • ∆t • Plant Supply / Return • P + I Controls • PID Available
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Fundamentals of Hydronic Design
Construction
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Fundamentals of Hydronic Design
• Construction • Thermal “Capacitor” • Reduce Back and Edge Loss • “Power” Draw at Surface •Wind •Precipitation • Phase Change • Liquid • Vapor
Edge Loss: Think Retainer For Sand Box
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Fundamentals of Hydronic Design
Courtesy of American Iron and Steel Institute
• Construction • Sub Grade •Structural Loads •Live and Dead Loads •Soil Stability •Compaction/Compression •Moisture/ Water Table • Insulation
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Fundamentals of Hydronic Design
• Construction • Sub Grade •Excavation •Undisturbed •Compacted •Drainage
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Fundamentals of Hydronic Design
• Construction • Moisture •Water Table •Run Off •Melted Snow •Splash
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Fundamentals of Hydronic Design
Source: National Radiant Design Center
• Construction • Insulation
• Think Moisture • Think Freezing • Think Soil Expansion • Think Heaving/Swell • Think Collapse/Shrink
•Do Control Heat •Do Control Moisture
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Fundamentals of Hydronic Design
• Construction • Insulation •Asks where do you want heat to flow, when and how fast?
Source: 2000 ASHRAE Handbook, Systems and Equipment copy written © 2005, by the American Society of Heating, Refrigerating and AirConditioning Engineers, Inc. (www.ashrae.org).
Reprinted with permission from ASHRAE Applications Handbook.
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Fundamentals of Hydronic Design
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Fundamentals of Hydronic Design
Courtesy of American Iron and Steel Institute
• Construction • Structure • Compacted Base • Reinforcement • Air Entrained Concrete Sloped ¼” per Ft • 4000psi @ 28 days • .50 h 2 o to cement
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Fundamentals of Hydronic Design
• Construction • Structure • Compacted Base • Reinforcement • Air Entrained Concrete Sloped ¼” per Ft • 4000psi @ 28 days • .50 h 2 o to cement Curing Temperature, ˚F
40 60 80 100 120
6
5
4
3
2
1
0 Com
pressive Stre
ngth, 1000 psi At 28 Days
At 1 Day
Design and Control of Concrete Mixtures, Portland Cement Association, 2003
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Fundamentals of Hydronic Design
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Fundamentals of Hydronic Design
Courtesy of American Iron and Steel Institute
• Construction • Structure •Control Joints •Lesser of • Min 2 x width or every 15ft • ∆ in direction or elevation
•Tube Placement & Pattern • Critical • Influences • Pick Up & Back Loss
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Fundamentals of Hydronic Design
Courtesy of American Iron and Steel Institute
• Construction • Surface •Bull Floated •Surface Water Evaporated •Depth of Control Joints • 25% of slab thickness
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Fundamentals of Hydronic Design
• Construction • Joints • Control, Expansion, Construct
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Fundamentals of Hydronic Design
Calculations
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Fundamentals of Hydronic Design
• Calculations • Academic Exercise • Ensures equipment and construction can deliver when called upon if and when the “predicted” event happens.
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Fundamentals of Hydronic Design
• Calculations • Is the System for Protection • Is the System for Convenience • Both • Load Calculation ( See Heat Loss to Head Loss, R.Bean, R.E.T., RPA Report) •Thermal Calculations •Hydraulic Calculations •Energy Estimate Calculation
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Fundamentals of Hydronic Design
• Calculations • Convective • Evaporation • Conductive • Radiative
Wet Dry
Earth
Conduction
Fire
Radiation
Hot
Cold
Air
Convection
Water
Evaporation
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Fundamentals of Hydronic Design
• Calculations • Convective & Evaporation •Wind Velocity •Characteristic Dimension • Shorter slabs have higher convective losses •Wind blown parallel to the long dimension has less load than if the wind blows perpendicular to the longest length.
•Elevation
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Fundamentals of Hydronic Design
• Calculations • Conductive •Slab Temperature at the Start of Melting •Snow Density •Rate of Snow Fall
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Fundamentals of Hydronic Design
• Calculations • Radiative •Effective Sky Temperature • Dry Bulb Air Temperature • Humidity • % of cloud cover
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Fundamentals of Hydronic Design
• Calculations • Radiant Loss •Cloud Cover Temperature •standard lapse rate • 3.5°F per 1000 feet •@10,000 ft = 35 ˚F
•assumed to be opaque
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Fundamentals of Hydronic Design
• Calculations • Back Losses •Depends on: • On/off • Idle/On • Ground Temps • Construction • Insulation • Tube Placement
•As high as 50%
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Fundamentals of Hydronic Design
• Calculations • Wind •Reduces melting capacity •Direction and slab dimension •10 Mph may add 50% to load •Causes drifting snow • Is the slab on? • Is it idling? • Is it off?
•System Performance
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Fundamentals of Hydronic Design
• Calculations • Snow Density • Weather Bureau • 90% of Snow Fall • Occurred between 10˚F and 35˚F
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Fundamentals of Hydronic Design
Outdoor Temperature, °F.
Weight (lbs/ft 3
)
0 8 10 12 14 16 18 20 22 24 26 28 30 32 34 2 4 6 0
7
6
4
3
5
8
1
10
2
9
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Fundamentals of Hydronic Design
• Calculations • During Snow Fall • q o =( q m + q s ) + ( Ar x ( q h + q e )) • q o ,Power per unit area • q m, ,Intensity of heat of fusion (phase change, snow to water) • q s ,Intensity of sensible heat transferred to snow (snow to 32˚F) • Ar ,Area ratio (how much surface area is permitted to accumulate snow) • q e ,Intensity of heat of evaporation (natural evaporation of melted snow) • q h ,Intensity of heat loss to atmosphere (from snow free areas)
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Fundamentals of Hydronic Design
• Calculations • After Snow Fall • q o = q ha + q ea • q ha = Intensity of surface heat loss to atmosphere after snowfall • q ea = Intensity of heat of evaporation after snowfall
• During Idling • q o = q i ( Idling load where qe≈0)
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Fundamentals of Hydronic Design
• Calculations • Fluid Temperature •Variations w/in Literature •Adlam / Kilkis / Spitler et al •ASHRAE / IBR •Software • From Research Projects • Manufactures • 3 rd Party Developers
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Fundamentals of Hydronic Design
• Calculations • Fluid Temperature •Adlam/ASHRAE for ¾” steel pipes @ 12” o.c., 2” depth •Flux / 2 + t f ˚F = t avg • t f ˚F = film temperature ≈ 33˚F •Example •(140 Btu/h/ft 2 ÷ 2) + 33˚F = 103˚F avg. •t s = (∆t/2) + t avg = (25˚F/ 2) + 102˚F ≈ 115˚F supply
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Fundamentals of Hydronic Design
• Calculations • Fluid Temperature • t f = [ρ×c p ×Q j ×∆t/c] 1/n + t a
• t f , Fluid temperature • ρ, Fluid density, • c p , Specific heat • Q j , Volumetric fluid flow rate in branch • ∆t, Temperature drop • c, Unit heating capacity • n, Power of the equipment heating capacity • t a , air temperature wetting the heat transfer surface
Reference Source: An Analytical Algorithm for Hydronic Circuit Analysis and Assessment of Equipment Performance
Birol Ì. Kilkis, Ph.D., Fellow ASHRAE
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Fundamentals of Hydronic Design
• Calculations • Fluid Temperature •FEA Software
Source: Development of a Two Dimensional Transient Model of SnowMelting Systems, and Use of the Model for Analysis of Design Alternatives, ASHRAE 1090RP, 2001
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Fundamentals of Hydronic Design
• Calculations • Software •Weather •Construction •Expectations •Controls
Copyright 2004, American Society of Heating, Refrigerating and Air Conditioning Engineers, Inc. and Oklahoma State University.
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Fundamentals of Hydronic Design
American Iron and Steel Institute
• Calculations • Example •2” Tube Depth •5/8” PEX •8” Spacing • Insulated •130˚F Average
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Fundamentals of Hydronic Design
Copyright 2004, American Society of Heating, Refrigerating and Air Conditioning Engineers, Inc. and Oklahoma State University.
< Mass of Ice
Height of Snow> Free Area Ratio >
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Fundamentals of Hydronic Design
Copyright 2004, American Society of Heating, Refrigerating and Air Conditioning Engineers, Inc. and Oklahoma State University.
Temperature,˚F Heat Flux, Btu/h ft 2
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Fundamentals of Hydronic Design Applications Other Than Snow
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Fundamentals of Hydronic Design Copyright / References/ Acknowledgements •Graphic, American Iron and Steel Institute, © Copyright, All Rights Reserved. Graphic, National Radiant Design Center, © Copyright, All Rights Reserved. •Graphic, Building Science Corporation, © Copyright, All Rights Reserved. •Graphic, Boston Aerial Highway 1958 © The Aberdeen Group, All Rights Reserved •Modern Hydronic Heating, J. Siegenthaler, © Copyright, All Rights Reserved. •RPA Guidelines for the Design And Installation of Radiant Panel Heating and Snow/Ice Melt Systems (2004 Edition). © Copyright 2004, All Rights Reserved. •Development of a Two Dimensional Transient Model of SnowMelting Systems, and Use of the Model for Analysis of Design Alternatives, ASHRAE 1090RP, 2001, Spitler, Rees, Xia, Chulliparambil, American Society of Heating, Refrigerating and AirConditioning Engineers, Inc. and Oklahoma State University. Reprinted by permission from ASHRAE. © Copyright 2004, All rights reserved •A Simulation Tool for the Hydronic Bridge Snow Melting System, Liu,Spitler, Submitted to the 12th International Road Weather Conference, Oklahoma State University, School of Mechanical and Aerospace Engineering, © Copyright, All Rights Reserved. •An Analytical Algorithm for Hydronic Circuit Analysis and Assessment of Equipment Performance Kilkis, copy written © 2005, by the American Society of Heating, Refrigerating and AirConditioning Engineers, Inc
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Fundamentals of Hydronic Design Snow Melting, Adam, Napier, T, 1950
Heat Requirements of Snow Melting Systems, Chapman, W.P., Katunich, S., 1956
Snow Melting Calculation and Installation Guide, S40 for Residences, Hydronics Institute, 1991
Design of Embedded Snow Melting Systems Part 1 & 2, ASHRAE Transactions, Kilkis, 1994
Updating the Tables of Design Weather Conditions in the ASHRAE Handbook – Fundamentals, ASHRAE 890RP, 1998
Development of Snow Melting Load Design Algorithms Volume I, ASHRAE 926RP, 1999, Ramsey, Hewett, Kuen, Petersen, Spielman, Briefer,
Updated Design Guidelines for Snow Melting Systems, ASHRAE Transaction CH99172, 1999
Transient Analysis of SnowMelting System Performance, ASHRAE Transactions 4591 (RP1090), 1999, Spitler, Rees, Xia, Chulliparambil
Development of a Two Dimensional Transient Model of SnowMelting Systems, and Use of the Model for Analysis of Design Alternatives, ASHRAE 1090RP, 2001, Spitler, Rees, Xia, Chulliparambil
Wirsbo Snow & Ice Melting Design Manual, 2003
Copyright / References/ Acknowledgements: con’t w/ chronological resources
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Fundamentals of Hydronic Design
Radiant Based HVAC Systems
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