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Design Build Test Apparatus Cross Flow Heat Exchanger Scaled Building Air Conditioning System

Design Build Test Apparatus Cross Flow Heat Exchanger Scaled Building Air Conditioning System. Gustavo Calderon Debora Chavez Mauricio Vargas Manuel Rivera. Statement. Ethical Design Statement

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Design Build Test Apparatus Cross Flow Heat Exchanger Scaled Building Air Conditioning System

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  1. Design Build Test ApparatusCross Flow Heat ExchangerScaled Building Air Conditioning System Gustavo Calderon Debora Chavez Mauricio Vargas Manuel Rivera

  2. Statement • Ethical Design Statement This project’s final proposed design along with its corresponding design processes have been reviewed to conform to the Code of Ethics for Engineers as published by the ASME International.

  3. Table of Contents • Introduction • Problem Formulation • Design Tree • Cold Chamber Design • Duct System Testing Facility Design • Cross Flow Heat Exchanger Design • DBT Bill of Materials • Project Layout • Major Failure Considerations • Conclusions

  4. Introduction • Purpose of the project • NSF funded project

  5. Problem Formulation • Update a current piece of teaching equipment (PA Hilton Cross Flow Heat Exchanger Apparatus) • Design a facility that allows students to build and test designs of scaled air distribution duct systems in various building models

  6. Design Tree

  7. Cold Chamber • Purpose • Conditioning of the operating fluids • Specifications • 6 X 6 X 6 ft3 • 6 in Polystyrene insulation • 26 gauge galvanized steel sheeting on both sides • Operating temp = 0 F

  8. Components • Refrigeration system • Air coil • Water coil • Thermal storage • Fan

  9. Refrigeration System • Purpose • provides the necessary conditions in the chamber (0 F) • Specifications • Heatcraft Pro3 • Model PTN021L6A • Capacity 2680 Btu/h @ 0 F • CFM 350

  10. Air Coil • Purpose • Serves as heat exchanger to condition the air supplied to the box. • Design Conditions • Air entering temperature 70F • Air leaving temperature 45F

  11. Engineering Analysis • Relate the heat loss of the facility to the air design conditions • sensible heat lost by the air • The total heat transfer rate • External flow correlation • Internal flow correlation Results • Length 6 ft • Coil diameter 0.5 in

  12. Glycol Coil • Purpose • Condition and maintain glycol temperature • Alternatives • Close loop • Bank of tubes • Open loop (10 gallon tank)

  13. Design Conditions • Glycol entering temperature: in the range of (3-7) F • Air leaving temperature 0F • Flow rate - 2GPM • From load calculations: 2500 BTU/hr is needed to be removed. • Bohn low profile unit cooler from Heatcraft Inc • Model LET 035 • Capacity of 3,500 BTU • Fan CFM of 700

  14. Thermal Storage • Purpose • available refrigeration system cannot sustain the cooling load requirements (only 50 %) • Reduce cost and attempt to use alternative energy efficient methods • Principle • Stores the energy in a medium during off peak hours and delivers later at peak hours

  15. Specifications • Glycol (31.6 % by volume) and water mixture. • freezing point = 1.4 F, which is slightly higher than the cold chamber’s temperature of 0 F • The thermal storage will have to support the cold chamber with 8000 btu/hr in a period of two hours • Engineering Analysis • Latent heat • Sensible heat (neglected) • Approx. 22 gallons of brine solution4

  16. Total load on the cold chamber • loads on the chamber include heat generated by the working fluids, fan, and external environmental loads. • Heat loss due to convection and conduction • Radiation negligible

  17. Summary of Results

  18. Duct System Testing Facility (DSTF) • Purpose • Test open-ended duct system designs and evaluate overall layout • Prototype of real warehouse • Functions • Air conditioning • Air supply • Control Features • Components • Compressor • Mixing module • Envelope

  19. Compressor • Purpose • provide the necessary flow rate and pressure of the air that has to be supplied into the DSTF chamber • Bernoulli’s equation • Pressure range required (1-5 psi)

  20. Separation of Air flow

  21. Mixing Module • Temperature is controlled by mixing ambient room air with cold chamber air • Valves and thermocouples • Y fitting (brass)

  22. Data Acquisition

  23. Envelope • Dimensions 3 x 5 x 3 • Plexiglass ¼ in • Design Conditions • Supply temperature range 47 – 49F • Indoor (inside) Condition 55F

  24. Engineering Analysis • Cooling Load requirement • Envelop losses due to temperature difference • Conduction and convection • 600Btu/hr • Flow rate requirement • Sensible heat equation • Apply design conditions • 40 CFM

  25. Duct system Support • Alternatives • False Ceiling • Velcro Ceiling • Proposed Design • Plexiglass strip-head board

  26. Pipe Delivery System • Entire tubing outside of the cold chamber • Diameter 0.5 in • Flexible PVC

  27. Engineering Analysis • Determine the heat gain by the fluids as they flow from the cold chamber into their respective section.

  28. Air Summary of Results Glycol Solution

  29. Cross Flow Heat Exchanger Objective • As proposed in the CCLI the CFHE section of this project has the purpose of updating an existing piece of teaching equipment. • This involves adding a coolant fluid loop and removable test sections. • Updated apparatus will allow students to design and build evaporator circuitries and validate their designs through testing.

  30. Cross Flow Heat ExchangerExisting Equipment • Existing teaching apparatus: PA Hilton Cross Flow Heat Exchanger. • Allows students to conduct heat transfer coefficient experiments. • Features two independent variables: air flow velocity, placement of test element within the test section. • Existing equipment lacks the capability of flexible experimental setups.

  31. Cross Flow Heat ExchangerDesign Specifications • Allow students to design, build, and test evaporator circuitries. • Student Test Section (STS) must accept coil components of different diameters, in varied arrangements. • Coil components shall be easily assembled and provide watertight seal at all connections. • Refrigerant delivery system must provide conditioned refrigerant to STS in an effective and secure method. • Air flow conditioning equipment is needed to raise ambient air flow temperature inside the air duct. • Data acquisition probes must be provided to gather all relevant experimental data. • Refrigerant spill prevention methods must be devised. • Updated STS shall allow for original convection coefficient experiment to be performed.

  32. Cross Flow Heat ExchangerEngineering analysis • To design or predict the performance of a heat exchanger, it is necessary to relate the total heat transfer rate to design parameters such as inlet and outlet fluid temperature, overall heat transfer coefficient, and the total surface area. • The CFHE was modeled as a bank of tubes. • Zhuskauskas correlation was used to calculate the average heat transfer coefficient of a fluid flowing across a tube bundle The following assumptions were made: • The Reynolds number was based on maximum fluid mean velocity occurring within the coil which depends on the circuitry configuration. • There is a negligible effect on the thermo physical properties of air due to the temperature change.

  33. Cross Flow Heat ExchangerEngineering Analysis Zhuskauskas correlation: • NuD = Nusselt Number • RaD = Rayleigh Number • Pr = Prandtl Number

  34. Cross Flow Heat ExchangerEngineering Results

  35. Cross Flow Heat ExchangerEngineering analysis Aligned configuration:This configuration features 20 copper tubes for both ½ in. and 3/8 in. tube aligned arrays. For this particular arrangement a 0.7 St to SL ratio is recommended to ensure optimum air flow. Staggered configuration: This configuration features 18 copper tubes for both ½ in. and 3/8 in. tube aligned arrays. No placement ratio was followed since the staggered array naturally induces turbulent air flow across the tube bank.

  36. Cross Flow Heat ExchangerEngineering Analysis Results ½ in. Aligned configuration V = 4 (m/s) Np = 5 Do = ½ (in) ∆Tair = 6.5 to 11 Fo

  37. Cross Flow Heat ExchangerEngineering Analysis Results ½ in. Staggered configuration V = 4 (m/s) Np = 5

  38. Cross Flow Heat Exchanger½ in. tube Heat Exchange Circuitry Arrangements • Five total circuitry arrangements were considered in the analysis. • These varied configurations serve to illustrate the flexibility of the newly updated Student Test Section.

  39. Cross Flow Heat Exchanger3/8 in. tube Heat Exchange Circuitry Arrangements

  40. Cross Flow Heat ExchangerAir Pressure Drop Calculations Where X is the correction factor and f is the friction factor

  41. DBT Project Bill of Materials

  42. DBT Project Bill of Materials

  43. Major Failure Considerations • ECTA Glycol Leakage • Heater failure • Refrigerant leakage from refrigeration system • Unstable plexi-glass panel • Cold chamber structural failure

  44. Conclusions • Cold chamber was successfully designed with a thermal storage in view of the constraints • A scaled-down model of a building warehouse was designed using a plexiglas and a mixing module for proper conditioning of the space

  45. Questions? Thank you

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