lecture objectives n.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Lecture Objectives: PowerPoint Presentation
Download Presentation
Lecture Objectives:

Loading in 2 Seconds...

play fullscreen
1 / 19

Lecture Objectives: - PowerPoint PPT Presentation


  • 124 Views
  • Uploaded on

Lecture Objectives:. Finish with Solar Radiation and Wind Define Boundary Conditions at Internal Surfaces. Solar radiation. Direct Diffuse Reflected (diffuse). Solar Angles. q z. - Solar azimuth angle – Angle of incidence. Direct and Diffuse Components of Solar Radiation.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Lecture Objectives:' - adanne


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.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
lecture objectives
Lecture Objectives:

Finish with Solar Radiation and Wind

Define Boundary Conditions at Internal Surfaces

solar radiation
Solar radiation
  • Direct
  • Diffuse
  • Reflected (diffuse)
solar angles
Solar Angles

qz

  • - Solar azimuth angle
  • – Angle of incidence
hw1 problem

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

solar components
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:

external convective heat flux presented model is based on experimental data ito 1972
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

boundary conditions at external surfaces
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

wind direction
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

internal boundaries
Internal Boundaries

Internal sources

Window

Transmitted

Solar radiation

surface to surface radiation
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

internal heat sources occupants lighting equipment
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
internal heat sources
Internal Heat sources
  • Lighting systems
    • Source of convective and radiative heat flux
    • Different complexity for modeling
surface balance
Surface Balance

For each surface

– external or internal :

All radiation components

Conduction

Convection

Convection + Conduction + Radiation = 0

air balance convection on internal surfaces ventilation infiltration
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