Heather Instasi Tulio Borel

Objectives Design a radiant heating system for a greenhouse located in Atascadero, CA Hot ethylene-glycol solution flowing in tubes embedded in 20ft x 40 ft concrete foundation Keep greenhouse air around 68 °F

Process Calculate heat loads based on greenhouse geometry Select spacing and diameter of tubing and number of coils 2D conduction model Find heat transfer, flow rate, temperatures, pressure drop in each coil Find total pressure drop Select a pump, heat exchanger, boiler, expansion tank Cost estimation

2D Conduction Model Things to consider: Pressure drop Cost Even heating

System Layout Drawing

Total System Pressure Drop Include: Heat Exchanger Pressure Drop (2.42 lbf/in 2 ) Pressure drop due to fittings (elbows & tees—branch and line flow) ( lbf/in 2 ) Pressure drop in each coil (3.715 lbf/in 2 ) Pressure drop in pipe connecting mechanical room & greenhouse ( lbf/in 2 ) Pressure drop between boiler and heat exchanger in mechanical room (0.028 lbf/in 2 ) Total = lbf/in 2

Pump Selection Operating Point: gpm ft of Head

Heat Exchanger Selection Need at least Btu/hr heat transfer rate SEC PL/PLT 70 Heat Exchanger produces Btu/hr Temperature difference of 15.5 °R on boiler side Flow Rate 3373 lbm/hr (25L/min)

Boiler Selection Utica MGB-125J Input Rate: Btu/hr Heating Capacity: Btu/hr Efficiency: 82% Bypass flow rate: gpm

Expansion Tank Selection Flexcon 2.1 gallon tank Total volume needed = gallons

Cost Analysis Total capital cost: $13172 Insulation cost Operating Costs Boiler: $3321/yr Pump: $19.44/yr Present worth analysis for 15 years at 6% interest rate: $45,613 Electric system PW analysis: $85163 Electric system is 86% more expensive Insulation Thickness (in) Area of Insulation (ft^2) Heat Transfer Loss (Btu/hr) Capital Cost ($) Operating Cost in a year ($/yr) O.C in 15 year Life Cycle ($) Figure 1: Insulation Cost Analysis