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 - VAV design (2 teams) -DOAS design/analysis Cooling systems Chiller and Cooling tower Performance analysis (2 teams)

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

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

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

Heat transfer in a building

Cooling Loads - UNSTEADY STATE Use Design Weather Data Detail method Requires complex calculation 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

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.

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

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.

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 ath.pdfhttp:// ath.pdf egoryID=58http:// egoryID=58

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