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Environmental Systems and Facilities Planning

Environmental Systems and Facilities Planning. Doug Overhults University of Kentucky Biosystems & Agricultural Engineering. University of Kentucky College of Agriculture. Topic Outline. Psychrometrics Review Energy Balances/Loads Latent heat Sensible heat Solar loads

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Environmental Systems and Facilities Planning

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  1. Environmental Systemsand Facilities Planning Doug Overhults University of Kentucky Biosystems & Agricultural Engineering University of Kentucky College of Agriculture

  2. Topic Outline • Psychrometrics Review • Energy Balances/Loads • Latent heat • Sensible heat • Solar loads • Insulation Requirements

  3. Topic Outline • Ventilation Systems • Rate requirements • System requirements • Moisture Control Standards • Air Quality Standards • Humans • Animals • Plants and Produce

  4. Psychrometrics • Variables • Using the Psychrometric Chart • Psychrometric Processes

  5. Psychrometric Chart “Humidity” Scale or axis State Point Dry Bulb Temperature Scale (axis)

  6. Psychrometric Chart(temperatures + relative humidity) Example: 70 oF dry bulb 55 oF dew-point 61 oF wet-bulb 60 % rh relative humidity “Humidity” Scale dew-point wet bulb dry bulb Dry Bulb Temperature Scale

  7. Psychrometric Processes • Heating, cooling, humidifying, dehumidifying air-water vapor mixtures • Five basic processes to know • Heat or Cool (horizontal line) • Humidify or De-humidify (vertical line) • Evaporative cooling (constant wet-bulb line)

  8. Heating: dry bulb increase “Humidity” Scale Horizontal line means no change in dew-point or humidity ratio ending state point starting state point Dry Bulb Temperature Scale

  9. Humidification: dew-point increase “Humidity” Scale Vertical line means no change in dry bulb temperature RH goes up! end state start state Dry Bulb Temperature Scale

  10. Evaporation: wet bulb increase “Humidity” Scale Increase in vertical scale: humidified Decrease in horizontal scale: cooled end state Constant wet bulb line start state Dry Bulb Temperature Scale Adiabatic process – no heat gained or lost (evaporative cooling)

  11. Air Density “Humidity” Scale Wet bulb line Humid Volume, 1/ ft3/lb da Dry Bulb Temperature Scale

  12. Review • Name three temperature variables • Name three measures of humidity • Name the two main axes of the psychrometric chart • Name the line between fog and moist air • Heating or Cooling follow constant line of ? • Humidify/Dehumidify follow constant line of ?

  13. Energy and Mass Balances

  14. Energy and Mass Balances • Heat Gain and Loss • Latent and Sensible Heat Production • Mechanical Energy Loads • Solar Load • Moisture Balance

  15. Heat Gain and Loss • Occupants • Lighting • Equipment • Ventilation • Building Envelope • Roof, walls, floor, windows • Infiltration (consider under ventilation)

  16. Heat Loads • Occupant (animals, people) • Sensible load (e.g. Btuh/person) • Latent load (“) • Lighting, W/m2 • Appliance W/m2 • Ventilation air (cfm/person or animal) • Equipment (e.g. Btuh for given items)

  17. Building Ventilation Rate • Temperature control • Moisture control • Contaminants (CO2, dust, NH3) control • Need data for heat, moisture, or contaminant production in building • Energy use – VR is a major variable

  18. Latent and Sensible Heat Production • Example from ASAE Standard EP270.5: Table 1. Moisture Production, Sensible Heat Loss, and Total Heat Loss CattleBldg. TMPSHLTHL 500 kg 21C 1.3 gH2O/kg-h 1.1 W/kg 2.0 W/kg

  19. Sensible Energy Balance • Leads to Ventilation for Temperature Control: qs + qso + qm + qh= ΣUA(ti-to) + FP(ti-to) + cpρV (ti-to) Heat inputs = envelope + floor + ventilation U – building heat transfer coeff. P – floor perimeter F – perimeter heat loss factor cp – specific heat of air V – ventilation rate ρ – density of air qs – sensible heat qso – solar heat gain qm – mechanical heat sources qh – supplemental heat

  20. Sensible Energy Balance • Leads to Ventilation for Temperature Control. Rearranging: V = [ qs - (ΣUA+ FP)(ti-to)] / 0.24 ρ(ti-to)60 V – cfm (equation for English units)

  21. Mass Balance Moisture, CO2, and other materials use balance equations. mp Material produced mvi Material input rate mvo material output rate + =

  22. Moisture Balance Example balance for moisture control removal rate. / mair Ventilation rate Mwater Moisture to be removed (Wi-Wo) Humidity ratio difference = Q = (V / 60) x [ Wr / (Wi-Wo) ] Q - cfm V – ft3/lbdaWr – lbm / hr W – lbm / lbda

  23. Moisture Balance Find the minimum winter ventilation rate to maintain 60% relative humidity inside a swine nursery that has a capacity of 800 pigs weighing 10 pounds. Inside temperature is 85 degrees. ASABE D270.5 Nursery Pigs Bldg. TMPSHLTHL 4 - 6 kg 29C 1.7 gH2O/kg-h 2.2 W/kg 3.3 W/kg

  24. Find the minimum winter ventilation rate to maintain 60% relative humidity inside a swine nursery that has a capacity of 800 pigs weighing 10 pounds. Inside temperature is 85 degrees. • Find moisture production data • ASABE Standards (EP270.5) • Wr= 0.017 lb/hr/pig • Get psychrometric data from chart • W0 = 0.0005 • Wi = 0.0154 • V = 14.1

  25. Moisture Balance / mair Ventilation rate Mwater Moisture to be removed (Wi-Wo) Humidity ratio difference = Q = (V / 60) x [ Wr / (Wi-Wo) ] • Put data into equation & solve • Q = (14.1/60) x [(.017 x 800) / (.0154 - .0005)] • Q = 214 cfm

  26. NH3 Balance Find the ventilation rate required to prevent the ammonia concentration inside a poultry layer barn from rising above 20 ppm. Ammonia production in the barn is estimated to be 21.6 cubic feet per hour. Ammonia concentration in the ambient air is 2 ppm.

  27. NH3Solution • Use volumetric form of mass balance equation • Vp + Vi = Vo • Vp + Qv[NH3]i = Qv[NH3]o • Solve for Qv • Qv = Vp / { [NH3]o - [NH3]i } • Volumetric NH3 production rate per minute • Vp = (21.6 ft3/hr / 60 min/hr) = 0.36 ft3/min • Plug into equation & solve • Q = 0.36 / (.000020 - .000002)] • Q = 0.36 / .000018 • Q = 20,000 cfm

  28. Energy Balance What is the ventilation rate for a swine finishing barn that will limit the design temperature rise inside the house to 4 degrees (F) above the ambient temperature? The barn capacity is 1000 pigs at 220 pounds and the inside temperature is approximately 85 F. The overall heat transfer coefficient for the barn is 1200 Btu/hr F.

  29. What is the ventilation rate for a swine finishing barn that will limit the design temperature rise inside the house to 4 degrees (F) above the ambient temperature? The barn capacity is 1000 pigs at 220 pounds and the inside temperature is approximately 85 F. The overall heat transfer coefficient is 1200 Btu/hr F. • Find heat production data • ASABE Standards (EP270.5) • q = 0.49 W/kg (sensible heat) • Convert units & calculate total heat load • q = 0.49 W/kg x 100 kg/pig x 1000 pigs • = 49,000 W x 3.412 Btu/hr W • = 167,188 Btu/hr • Density of Air = 0.075 lb/ft3 • Specific heat of air = 0.24 Btu/lb F • ti – to = 4 F

  30. Continuation . . . ventilation rate for a swine finishing barn that will limit the design temperature rise inside the house to 4 degrees (F) above the ambient temperature • Basic equation • Neglect floor heat loss or gain • Plug into equation & solve • V = [167,188 - (1200 x 4)] / [(0.24 x 0.075) x 4 x 60] • V = 37,590 cfm V = [ qs - (ΣUA+ FP)(ti-to)] / 0.24 ρ(ti-to)60

  31. Insulation • Building Heat Loss • Qb = (A/R)T x ∆t • (A/R)T = sum of all (area/resistance) ratios for all components of the building i.e. walls, ceiling, doors, windows, etc.

  32. Insulation Wall Section - Resitances in Series

  33. Insulation & Heat Loss Need R-value for each component

  34. Insulation & Heat Loss • Qb = (A/R)T x ∆t (Btu/hr) • Walls - Qw = (Aw/Rw) x ∆t • Doors - Qd = (Ad/Rd) x ∆t • Ceiling - Qc = (Ac/Rc) x ∆t • Proceed through all components • Perimeter is special case • R-value is per unit of length - essentially assumes a 1 ft width along perimeter • Qp = (Lp/Rp) x ∆t

  35. Building Heat Loss • Qbldg = (A/R)w x ∆t + (A/R)d x ∆t + (A/R)c x ∆t + . . . . . • ∆t is the same for all components • Qbldg = (Ai/Ri) x ∆t • (A/R)Total = (Ai/Ri) sum of all (area/resistance) ratios for all components of the building i.e. walls, ceiling, doors, windows, etc. • Qbldg = (A/R) Total x ∆t

  36. Insulated Wall Problem The wall of a poultry house will be insulated on the inside by adding 2 inches of spray foam insulation. The R-value of the spray foam insulation is 6 per inch of thickness (hr ft2 F/Btu in). R-values for the top 1/3 and bottom 2/3 of the existing wall are 12 and 6 (hr ft2 F/Btu), respectively. No other changes are made. What is the heat loss through the wall after the foam insulation is added as a fraction of the heat loss through the existing wall?

  37. Insulated Wall Solution R-value of added insulation (2 inches) Rfoam = 2 x 6 = 12 New R-values Rupper = 12 + 12 = 24 Rlower = 12 + 6 = 18 No area given – solve for a unit area (1/3 upper & 2/3 lower)

  38. Insulated Wall Solution What is Qafter/Qbefore No ∆t given but no change between before & after The end result is a ratio of heat losses, so ∆t will be the same in numerator & denominator. All that remains is a ratio of the new & old A/R values. Existing – Wall A/R = 0.33/12 + 0.67/6 = 0.139 New – Wall A/R = 0.33/24 + 0.67/18 = 0.051 Ratio New/Old = 0.051/0.139 = 0.367

  39. Fan Operating Cost Electrical Power Cost V Ventilation volumetric flow rate W Power input, Watts cfm / Watt Fan Test Efficiency = ÷

  40. Calculate Operating Costs • Design Ventilation Rate – 169,700 cfm • Fan Choices • Brand A – 21,300 cfm @ 19.8 cfm/watt • Brand B – 22, 100 cfm @ 16.2 cfm/watt • Fans operate 4000 hours per year • Electricity cost - $0.10 per kWh • Calculate annual operating cost difference

  41. Calculate Operating Costs • Determine number of fans required • Brand A - 169,700/21,300 = 7.97 • Brand B - 169,700/22,100 = 7.68 • 8 fans required for brand A or B

  42. Calculate Operating Costs • Use EP 566, Section 6.2 • Annual cost is for all 8 fans Watts * hrs * $/kWh * kWh/Wh = $

  43. References – Env. Systems • Albright, L.D. 1990. Environment Control for Animals and Plants. ASAE • Hellickson, M.A. and J.N. Walker. 1983. Ventilation of Agricultural Structures. ASAE • ASHRAE Handbook of Fundamentals. 2009.

  44. Reference MWPS - 32 Contains ASABE heat & moisture production data & example problems Midwest Plan Service Iowa State University Ames, IA

  45. Reference MWPS - 1 STRUCTURES and ENVIRONMENT HANDBOOK Broad reference to cover agricultural facilities, structures, & environmental control Midwest Plan Service Iowa State University Ames, IA www.mwps.org

  46. Useful References – Env Sys • MidWest Plan Service. 1990. MWPS-32, Mechanical Ventilation Systems for Livestock Housing. • Greenhouse Engineering (NRAES – 33) ISBN 0-935817-57-3http://palspublishing.cals.cornell.edu/nra_order.taf

  47. References – ASAE Standards • EP270.5 – Ventilation systems for poultry and livestock • EP282.2 – Emergency ventilation and care of animals • EP406.4 – Heating, ventilating cooling greenhouses • EP460 – Commercial Greenhouse Design and Layout • EP475.1 – Storages for bulk, fall-crop, irish potatoes • EP566 – Selection of energy efficient ventilation fans

  48. FACILITIESManure Management Example

  49. Manure Management Facilities • Animal Manure Production • Nutrient Production • Design Storage Volumes • Lagoon – Minimum Design Volume • References • ASAE – EP 384.2, 393.3, 403.3, 470 • NRCS – Ag. Waste Field Handbook

  50. Size a Manure Storage • 1 year storage • Above ground 90’ dia. tank – uncovered • 2500 hd capacity – grow/finish pigs • Building turns over 2.7 times/yr • Manure production 20 ft3/finished animal • Net annual rainfall = 14 inches • 25 yr. – 24 hr storm = 5.8 inches

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