All Lectures

E fresh air burner electricity heat cooling unit

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: nsport energy Consider the HVAC system for the theoretical building described in Mini-Project A… Schematic Representation of the Simulated HVAC System Single Duct System providing 3 functions: • delivery of cooling air Natural Gas Reject Heat • delivery of heating air Flue Gases • delivery of ventilation air (i.e. fresh air) Burner Electricity Heat Cooling Unit Outdoor Air Economizer (not shown) Furnace HX’er Electricity Note: constant-volume supply-fan (for selected system type) Mixed Air Recirculated Air Cooling Coil Heating Coil Supply Fan + Motor Supply Air Exhaust Air Thermal Zone Return Air T Baseline Energy Result: Baseline Energy Result: Annual Energy Costs by End-Use $1,200 Total: $3,038 $1,000 $800 $600 $400 $200 $0 Interior Lights Energy Costs: Misc Equipment Space Heating Space Cooling Electricity = $0.10/kWh HVAC HVAC Fans Hot Water Auxiliary Natural Gas = $0.70/therm Detailed Simulation Output: Baseline: Some information from Detailed Output Report 182 kbtu/hr electrical power input = 1.054 kW 76 kbtu/hr Outdoor Air 2667 cfm Mixed Air 501 cfm Cooling Coil Heating Coil Supply Fan Supply Air Recirculated Air Exhaust Air Thermal Zone Return Air = ∆ ∙ T efficiency of the series of devices converting electrical power to “air-power” annual fan “on hours” check annual fan energy… = ∙ ∆ = (1.054 #$ )(3000 '() Factors determining simulated fan-motor power consumption? flow? ∆ ∙ air-flow rate needed to meet peak cooling load (plus oversizing) 2667 cfm Outdoor Air Mixed Air 501 cfm Cooling Coil Heating Coil Supply Fan Supply Air Recirculated Air Exhaust Air Return Air Thermal Zone T In this particular simulation, the cooling design-condition has the greatest air-flow requirement and therefore determines the required air flow rate. Some Design Parameters affecting required air-flow rate: Outdoor Air Mixed Air Cooling Coil Heating Coil Supply Fan Supply Air Recirculated Air 55℉ Exhaust Air Return Air 75℉ Thermal Zone Approximate Cooling Effect Provided to Thermal Zone (i.e. energy balance on the thermal zone) + = - ∙ './ − ' = ∙ 1 ∙ './ − ' , volumetric flow rate + = ∙ 1 ∙ './ − ' cooling required = + 1 ∙ './ − ' selected air conditions (designer selected) air-flow rate required for peak cooling load For a fixed set of selected air conditions: • If peak cooling load increases, provided air flow must increase. • If peak cooling load decreases, provided air flow can decrease. Some Contributors to Peak Cooling Load in the Simulated Space? Hour of greatest space cooling load during the simulated year: Note: Space Load is not the same as cooling coil load. ASIDE: Heat Gains that may affect coil load? OUTDOOR AIR FAN HEAT Mixed Air 501 cfm Cooling Coil Heating Coil Supply Fan Supply Air Recirculated Air 2667 cfm PLENUM HEAT GAIN Exhaust Air Ceiling Space (return air plenum) Return Air Thermal Zone SPACE HEAT GAIN T (End of aside.) Simulate an energy efficiency upgrade that also reduces peak cooling load: • Improved Lighting Design (approx 30% lower overall) Baseline Upgrade Simulation Results: Annual Energy Costs by End-Use $1,200 Baseline (Total = $3,038) $1,000 Upgraded Lights (Total = $2,734) $800 $600 $400 $200 $0 Interior Lights Misc Equipment Space Heating Space Cooling HVAC HVAC Fans Hot Water Auxiliary Upgraded: Some information from Detailed Output Report electrical power input = 0.983 kW 72 kbtu/hr Outdoor Air 2488 cfm Mixed Air 501 cfm Cooling Coil Heating Coil Supply Fan Supply Air Recirculated Air Exhaust Air Thermal Zone Return Air = T ∆ ∙ check annual fan energy… = ∙ ∆ = (0.983 #$ )(3000 '() Impact of this particular load reduction?? $1,200 Baseline Upgraded Lights $1,000 $800 $600 $400 $200 $0 Interior Lights direct reduction in power consumption Misc Equipment Space Heating Space Cooling less waste heat (from lights & fan) HVAC HVAC Fans Hot Water Auxiliary lower airflow requirement; saves energy during every hour that constant-volume fan operates What about impacts on equipment cost? • power feed power to lights? (to fan motor?) • capacity of cooling coil/refrigeration unit? • capacity of supply fan? • duct sizes? • structural support for roof-top equipment? Incremental cost of upgrade?? energy delivered energy supplied pump/fan “transport” energy If flow-system designed to run at constant-flow based on peak-load, a reduction in peak load may save both “supply energy” and “transport energy” (and potentially reduce required equipment capacity). Recall: Compare the options or upgrading boiler efficiency or investing in insulation? wall U Ti boiler losses electricity baseboard heater boiler fuel pump piping 45 = 667 To Integrated Design Process • Design Team members working collaboratively to make decisions regarding investments in energy upgrades with consideration to the interactive effects of building components and systems. Usually employs detailed energy simulation to help guide the decision making process....
View Full Document

This note was uploaded on 10/04/2012 for the course ME 760 taught by Professor Davidmather during the Spring '12 term at Waterloo.

Ask a homework question - tutors are online