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Objectives

Objectives. Address Final Project Issues Learn/Review Cooling/Heating Load Calculation Procedure Compare Residential and Commercial Systems - Trends in residential HVAC. Final Projects. Residential System Operation Consequences of Oversized Cooling Coil Commercial Systems

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Objectives

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  1. Objectives • Address Final Project Issues • Learn/Review Cooling/Heating Load Calculation Procedure • Compare Residential and Commercial Systems - Trends in residential HVAC

  2. Final Projects • Residential System Operation • Consequences of Oversized Cooling Coil • Commercial Systems - VAV design (2 teams) • DOAS design/analysis • Cooling systems • Chiller and Cooling tower • Performance analysis (2 teams)

  3. Project Meetings • Discuss the scope and progress on the project • At least one member of the team • This Friday in PRC • Possible some other place and time

  4. Heating and Cooling Loads • Based on Building Physics • Heat and mass transfer thought building elements • NOT equal to energy consumption in building • First step in HVAC Design • Covered in 346N Building Environmental System Course • Chapter 14, 15, and 16 of your book • Computerized methodology • http://www.xpedio.carrier.com/idc/groups/public/documents/marketing/hap_ehelp_009.pdf • http://www.doe2.com/equest/ • http://tc47.ashraetcs.org/pdf/Presentations/Liesen_Chicago.pdf

  5. Heat loads - STEADY STATE Overall Idea • Use Design Weather Data • All terms will have units of power • BTU/hr or W • Two types of terms • Terms that are power (solar gain, internal gains) • Terms that need to be multiplied by an indoor/outdoor temperature difference • UA for conduction, MC for airflows

  6. Heat transfer in a building

  7. Cooling Loads - UNSTEADY STATE Use Design Weather Data Detail method Requires complex calculation - 365 days x 24 hours = 8760 hours - Heat and mass transfer through each building elements - Computer based calculation - Many available methods (tools) Two types of terms Identify the critical hour Simplify the method to use pre-calculated (tabulated) values - CLTD for heat transfer through opaque surfaces - SHGC for solar radiation through transparent surfaces

  8. LOAD vs. Energy Usage • Goal of heating/cooling/ventilation load is to design systems that • Can handle extreme conditions (through conservatism, not oversizing) • Operate efficiently at most conditions.

  9. Overall Strategy • Be conservative, not over-the-top • Use 1% values • Include all components • Focus on the components that are important • Be prepared to read about current practices

  10. Reference Table • Sources (unless otherwise indicated) are ASHRAE Handbook of Fundamentals (2005), Trost textbook, and other sources. • Your textbook is a fine source, but may not agree entirely with other sources.

  11. Residential Systems • Buildings are responsible for 40% of US energy use • ~1/3 houses • There will be a push for conservation in this sector • Zero Energy homes • http://www.eere.energy.gov/buildings/building_america/pdfs/29915_zeb_path.pdf • http://www.toolbase.org/ToolbaseResources/level3.aspx?BucketID=2&CategoryID=58

  12. Residential system • Technology is feasible and cost-effective • Several barriers to widespread use: • Up-front costs are still higher • Insufficient data on resale costs • Lack of experienced designers

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