A Neural Network based Zonal Method

Introduction

RAD-NNET-SG computes the radiation heat transfer from an arbritary area at the base in an arbritary enclosure to its bounding surfaces with a homogenous intervening CO2/H2O/N2/soot mixture at arbitrary mixture conditions (temperature, partial pressure of the participating gases and soot concentration).

The formulation of RAD-NNET-SG is based on the concept of Generalized Zonal Method (GZM) being introduced in Yuen & Takara (1995) for heat transfer problems in gray media and Tam & Yuen (2018) for fire simulation codes in non-gray media. The individual radiation calculation for two parallel rectangular surfaces and two perpendicular surfaces can be found in RAD-NNET-SSPP and RAD-NNET-SSPD, respectively.

The absorption of the mixture is computed using RAD-NNET which is a neural network developed based on narrow band spectral data provided by RADCAL. The detail of RAD-NNET and its associated references are presented in the RADNNET website.

Instructions for Run

The software requires 3 sets of input parameters:

The outputs of the software are:

  1. View Factor between Ai and Aj
  2. Exchange Factor between Ai and Aj
  3. Geometric Mean Transmittance between the Two Surfaces
  4. Total Emissivity of Gas (for emission to surface Ai)
  5. Total absorptivity of Gas (for emission from surface Ai at temperate Ts)
  6. Total radiative exchange between the gas and surface Ai
Note: This website calculates only the total emissivity and absorptivity of the gas relative to a single surface Ai at the floor of the enclosure. The total emissivity of the gas (accounting for emission to all direction) and the total absorptivity (accounting for absorption of radiation emitted by all surrounding boundary) can be obtained by superposition.

Instruction for a gray calculation

The program is setup with a "gray gas" option which can be triggered by specifying a negative value for the CO2 mole fraction. The value entered for the gas total pressure Pg will be interpreted as the absorption coefficient in unit of 1/m. The value entered for the soots volume fraction will be ignored.

Fill in Input Values: (Total Pressure = 1 atm (101 kPa))

Mixture Properties Inputs Valid Range Units
Soot Volume Fraction fv 0 to 0.000001 (-)
Gas Temperature Tg 300 to 2000 (K)
Mole Fraction of CO2 CO2/(CO2+H2O) 0.0 to 1.0 (-)
Gas Total Pressure Pg 0 to 101 (kPa)
Surface Temperature
Ts 300 to 1500 (K)

Enclosure Dimensions
Xroom (m)
Yroom (m)
Zroom (m)
Source Dimensions
X1 (m)
Y1 (m)
ΔX (m)
ΔY (m)

Download Results to File

Example 1

This example problem is used to demonstrate the setup of a simple radiation calculation with non-participating medium.

Taking the following inputs for mixture properties:

and the geometric configurations: You will have the following outputs:

Example 2

Using the geometry as shown in Example 1, a radiation calculation with typical combustion mixture is provided.

Taking the following inputs for mixture properties:

and the geometric configurations: You will have the following outputs:

All rights reserved. For more details, please contact Walter Yuen at yuen _at_ ucsb.edu or Wai Cheong Tam at waicheong.tam _at_ nist.gov. Last updated in Nov 2020.