1 / 19

Understanding Solar Radiation and Wind Effects on Internal and External Surface Conditions

This lecture covers key topics in solar radiation and wind effects on building surfaces. It defines boundary conditions at both internal and external surfaces, detailing direct, diffuse, and reflected solar radiation. Students will learn about solar angles, measurement techniques for solar radiation, and the importance of wind velocity and direction in energy simulations. The course utilizes experimental data and theoretical models to analyze heat flux across surfaces, incorporating factors like internal heat sources and the balance of radiation components for effective building energy performance.

aristotle-mcpherson
Télécharger la présentation

Understanding Solar Radiation and Wind Effects on Internal and External Surface Conditions

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Lecture Objectives: Finish with Solar Radiation and Wind Define Boundary Conditions at Internal Surfaces

  2. Solar radiation • Direct • Diffuse • Reflected (diffuse)

  3. Solar Angles qz • - Solar azimuth angle • – Angle of incidence

  4. Direct and Diffuse Components of Solar Radiation

  5. Measurement of Direct Solar Radiation

  6. Global horizontal radiation IGHRand Diffusehorizontal radiation measurements

  7. 2.5 m Internal surfaces 8 m 8 m HW1 Problem You will need Austin weather data: http://www.caee.utexas.edu/prof/Novoselac/classes/ARE383/handouts.html

  8. Solar components • Global horizontal radiation IGHR • Direct normal radiation IDNR Direct component of solar radiation on considered surface: Diffuse components of solar radiation on considered surface: qz Total diffuse solar radiation on considered surface:

  9. External convective heat fluxPresented model is based on experimental data, Ito (1972) Primarily forced convection (wind): Velocity at surfaces that are windward: Velocity at surfaces that are leeward: U -wind velocity Convection coefficient: u surface u windward leeward

  10. Boundary Conditions at External Surfaces 1. External convective heat flux Required parameters: - wind velocity • wind direction • surface orientation N leeward Consequence: U Energy Simulation (ES) program treatsevery surface with different orientation as separate object. windward

  11. Wind Direction Wind direction is defined in TMY database: “Value: 0 – 360o Wind direction in degrees at the hou indicated. ( N = 0 or 360, E = 90,   S = 180,W = 270 ). For calm winds, wind direction equals zero.” N http://rredc.nrel.gov/solar/pubs/tmy2/ http://rredc.nrel.gov/solar/pubs/tmy2/tab3-2.html leeward U windward Wind direction: ~225o

  12. Internal Boundaries Internal sources Window Transmitted Solar radiation

  13. Surface to surface radiation Exact equations for closed envelope Tj Ti Fi,j - View factors ψi,j - Radiative heat exchange factor Closed system of equations

  14. Internal Heat sourcesOccupants, Lighting, Equipment • Typically - Defined by heat flux • Convective • Directly affect the air temperature • Radiative • Radiative heat flux “distributed” to surrounding surfaces according to the surface area and emissivity

  15. Internal Heat sources • Lighting systems • Source of convective and radiative heat flux • Different complexity for modeling

  16. Surface Balance For each surface – external or internal : All radiation components Conduction Convection Convection + Conduction + Radiation = 0

  17. Air balance - Convection on internal surfaces + Ventilation + Infiltration Uniform temperature Assumption Affect the air temperature - h, and Q as many as surfaces - maircp.airDTair= Qconvective+ Qventilation Tsupply Qconvective= ΣAihi(TSi-Tair) Ts1 mi Qventilation= Σmicp,i(Tsupply-Tair) Q2 Q1 Tair h1 h2

  18. Distribution of transmitted solar radiationDIRECT solar radiation

  19. Distribution of transmitted solar radiationdiffuse solar radiation

More Related