Simulating Natural Ventilation in Indoor and Semi-Outdoor Spaces by Pratik Raval, Transsolar Climate Engineering

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January 10, 2013

Simulating Natural Ventilation in Indoor and Semi-Outdoor Spaces by Pratik Raval, Transsolar Climate Engineering

With the help of a couple of project examples, the talk will discuss different methodologies for simulating natural ventilation in indoor and semi-outdoor spaces. Beginning with the basic natural ventilation design concepts, the talk will focus on motivation, methodology, and goal of simulation appropriate for each project example.

About the Speaker

Pratik Raval is an expert in the fields of low-energy building physics and human comfort in built environments. As a project manager, he is responsible for developing and validating architecturally integrated climate responsive concepts and helps in designing comfortable built environments with minimal impact on natural environment. The scope of these concepts ranges from large scale master plan in desert climate to museum building with very stringent requirements in northern climate to high-rise office tower in tropical climate. He has been a part of many nationally and internationally recognized projects.

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January 10, 2013
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Transcript

  1. 1.

    1 Simulating Natural Ventilation in Indoor & Semi-Outdoor Spaces Pratik

    Raval Transsolar Inc. IBPSA-USA NYC chapter 10 January 2013 Simulating Natural Ventilation in Indoor & Semi-outdoor Spaces raval@transsolar.com
  2. 6.

    6 Natural Ventilation in a Semi-outdoor space Coupling Transient 3D

    Thermal Simulation with Detailed Multi-zone Airflow Model
  3. 7.

    7 Natural Ventilation in a Semi-outdoor space Natural Ventilation Mode

    Outdoor temperature: 55 – 78 °F Climate Concept
  4. 11.

    11 Natural Ventilation in Semi-outdoor space Coupling Transient 3D Thermal

    Simulation with Detailed Multi-zone Airflow Model
  5. 12.

    12 Natural Ventilation in Semi-outdoor space Simulation – Geometry Total

    volume : 198,500 ft³ Floor area : 5190 ft² Length : 109’ 8” (Greenhouse floor); 121’-6” (total west facade)
  6. 14.

    14 Natural Ventilation in Semi-outdoor space R-value of the backside

    wall & greenhouse floor 20 h-ft²-°F/Btu Curtain wall properties Overall U-factor (IGU+frame) 0.3 Btu/h-ft²-°F @ NFRC conditions Solar Heat Gain Coefficient 0.55 - 0.65 @ NFRC conditions Motorized horizontal fabric roller shades Control based on solar insolation as well as ambient and internal conditions in the winter garden System overall transmittance 7% Material reflectance (outer surface) 77% Material absorptivity 23% IR emissivity (inner surface) 50% Simulation – Boundary Conditions
  7. 15.

    15 Natural Ventilation in Semi-outdoor space Ventilation openings Closed during

    heating season (limited ventilation); Open during rest of the year Discharge coefficient when fully open 0.65 Flow reduction due to insect screen 30% Wind pressure coefficients considering sheltering effects from surrounding buildings Simulation – Boundary Conditions
  8. 16.

    16 Natural Ventilation in Semi-outdoor space Index for Comparison –

    Ambient Relative Indoor Degree-hours = � ("𝑙 𝑛𝑛𝑛 − ) "lower node">86°
  9. 24.

    24 Natural Ventilation in Indoor spaces Simulation !-------------------------------------------------------------------------------------- DATA READER

    - Hourly Sums + Mixes from Zones via Lastliste !-------------------------------------------------------------------------------------- PARAMS 38 1 !1 mode 2 !2 number of header lines to skip 8 !3 number of values to read from each line 1 !4 time interval of data [h] ! cycles for each variable to read (=num of columns): ! interpolate (1=yes, -1=no), multiplication factor, addition factor, data is avg (=0) or instantaneous (=1) values -1 1 0 1 -1 1 0 1 -1 1 0 1 -1 1 0 1 -1 1 0 1 -1 1 0 1 -1 1 0 1 -1 1 0 1 92 ! logical unit number for input file -1 ! free format mode (-1=free format) EQU 2 P_CL_Podium = [92,7] DeltaT = P_CL_Podium/(1.005*max(V_SOLAR,0.1)/3600)*Sched_OPR
  10. 25.

    25 Natural Ventilation in Indoor spaces Simulation DeltaP = rho

    * g * H * max((Tavg_chimney - Tamb),0)/(Tavg_chimney+273.15) EQU 4 DeltaP_1 = (1/(Cd_1**2)*(1/2)*rho*(V_SOLAR/(1.2*3600)/A_window)**2)*AND(GE(Tamb_m24,15),LE(Tamb_m24,26)) DeltaP_2 = (1/(Cd_2**2)*(1/2)*rho*(V_SOLAR/(1.2*3600)/A_Trans)**2)*AND(GE(Tamb_m24,15),LE(Tamb_m24,26)) DeltaP_3 = 1/(Cd_3**2)*(1/2)*rho*(V_SOLAR/(1.2*3600)/A_inlet)**2 DeltaP_4 = 1/(Cd_4**2)*(1/2)*rho*(V_SOLAR/(1.2*3600)/A_outlet)**2 EQU 1 !MODE INDICATOR: 1-WINTER PREHEAT, 2-NATURAL VENTILATION, 3-SUMMER NV =1*SCHED_OPR*LT(Tamb_m24,15)+ 2*SCHED_OPR*AND(GE(Tamb_m24,15),LE(Tamb_m24,26))+3*SCHED_OPR*GT(Tamb_m24,26)
  11. 29.

    29 Simulation Assumptions -10 -5 0 5 10 15 20

    25 30 35 40 18 20 22 24 26 28 30 32 34 Outside Temperature Inside Operative Temperature Frequency of Temperature Occurence NYC – Typical Indoor Operative Vs. Outdoor Temperature
  12. 30.

    30 -12 -10 -8 -6 -4 -2 0 2 4

    6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 0 100 200 300 400 500 600 Outdoor Temperature, °C Temperature Frequency (hours) Window Status - From 1/1/2012 to 8/29/2012 - vs Outdoor Temperature Open Closed Simulation Assumptions NYC – Typical Window Opening Behavior