Radiant Based HVAC Systems
Radiant Cooling & Heating
This educational material is copy written by Robert Bean, R.E.T., All Rights Reserved. If you wish to use this presentation for non commercial or for profit purposes, please contact info@healthyheating.com for details and restrictions. Portions of this presentation are copy written by others including materials copy written 2005, by the American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. (www.ashrae.org). Reprinted with permission from ASHRAE Applications Handbook. 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 Adobe s.pdf format.
Everything You Need to Know About Radiant You Learnt Before Kindergarten
Radiant Principles Thermography: Dr. Chapman (c/o Bob Hot Rod Rohr)
Radiant Principles Schlieren and shadowgraph: Dr. Gary Settles
Radiant Principles Software Modeling: Dr. decarli
Heat & Moisture Hot Air Convection Fire Radiation Wet Dry Water Evaporation Earth Conduction Cold
Thermal Comfort Dr. Fanger ANSI/ASHRAE Standard 55-2004 80% Satisfaction
Thermal Comfort Five Factors To Consider Activity Clothing Operative Temperature Humidity Air Speed
Operative Temperature is a combination of the air and surface temperatures in the space.
Radiant conditioned spaces have higher operative temperatures.
Humans like consistent temperatures between their ankles and head < 5 F t
Humans like floor temperatures above 66 F when cooling and below 84 F when heating.
Transmitted Absorb Long Wave Energy Reradiated Reflect Emit
Humans prefer drafts below 3 fps in heating and humidity between 30% and 70% rh.
Radiant Principles Demonstration of: ASHRAE Thermal Comfort Program V.1.0, by C. Huizenga, M.Sc., Berkley University, Dr. Fountain, Environmental Analytics Thermal Comfort Calculator by Dr. Marsh, Welsh School of Architecture at Cardiff University Thermal Comfort Test Facilities, Circa 1970, Lingby, Denmark Danish Technical University
ASHRAE Comfort Program
ASHRAE Comfort Program
SQU1 Comfort Program
We Condition People not buildings!
Radiant System Performance What happens from start up to steady state? What happens to thermal comfort performance when the architecture changes? How much heat we can deliver from a floor?
Radiant Principles Thermal Lag at Start Up With Radiant Systems the air is only warm Air Temp because the surfaces are warm! Temperature of Room Mass
Radiant Principles Thermal Lag at Start Recovery Is Fast Think Light Radiant Transfer occurs as Air Temp soon as there is a difference in temperatures. Temperature of Room Mass
Think Thermal Battery
A Note on Slab Insulation Soil Moisture Content (by Thermal Conductivity, Btu/h.ft. o F mass) Sand Silt Clay Low, <4% 0.17 0.08 0.08 Medium, 4 to 20% 1.08 0.75 0.58 High, > 20% 1.25 1.25 1.25 Table 3, Soil Thermal Conductivities, 2000 ASHRAE Systems and Equipment, pg 11.9 When it comes to specifying insulation types, the obligations of a professional designer are based on liability exposures. What is the standard of care expected from a design professional when specifying insulation? Are you below, at or above the benchmark in your decision? 2005, American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. (www.ashrae.org). Reprinted with permission from ASHRAE Applications Handbook. This article may not be copied nor distributed in either paper or digital form without ASHRAE s permission.
As you go through the next slides imagine you are in the space and it is heated with air.
As you go through the next slides imagine you are in the space and it is heated with radiant.
2) As cooler surfaces are warmed they reradiate to other cooler surfaces. 1) Radiant energy travels from a heated surfaces to cooler surfaces
By raising the temperature of all the surfaces we can counteract the effects of adding windows.
How much heat can we deliver from a radiant surface?
Radiant Systems Performance Output Examples - Typical Total Heat Exchange Coefficient Mode Heating Cooling Surface Btu/h ft 2 F W/m 2 ºK Btu/h ft 2 F W/m 2 ºK Floor 1.9 11 1.2 7 Wall 1.4 8 1.4 8 Ceiling 1.1 6 1.9 11 2005, American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. (www.ashrae.org). Reprinted with permission from ASHRAE Applications Handbook. This article may not be copied nor distributed in either paper or digital form without ASHRAE s permission.
Example For Radiant Heated Floors (85 o F 72 o F) x 2.0 Btu /sf / o F = 26 btu/sf floor output
1.1 1.9 1.4 Total Heat Exchange Coefficient Radiant plus Convective Btu/h ft2 F 1.4 1.9 1.2
Typical High Mass Poured Floor System
Typical Low Mass Channel Floor System
The Role of Water and Air In Thermal Comfort Forced-Air Heating Radiant Heating Hybrid Heating dp IAQ Room Air RH Occupant, Room Mass HRV PMV Occupant, Room Mass MRT Room Air AUST OT Comfort Conditions Satisfied Customers
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