The Working Gas function
The purpose of this function is to specify the values of the global variables relevant to the specific working gas choice - helium, hydrogen or air. The first 4 variables (rgas, cp, cv, gama) are required for the basic energy relations, and the last 4 variables (mu0, t0, t_suth, prandtl) are required in the Simple analysis for evaluation of heat transfer and flow friction of the working gas (refer to Chapter 5 - Scaling Parameters and Pumping Loss)
function gas % specifies the working gas properties (he, h2, air) % Israel Urieli 4/20/02 global rgas % gas constant [J/kg.K] global cp % specific heat capacity at constant pressure [J/kg.K] global cv % specific heat capacity at constant volume [J/kg.K] global gama % ratio: cp/cv global mu0 % dynamic viscosity at reference temp t0 [kg.m/s] global t0 t_suth % reference temperature [K], Sutherland constant [K] global prandtl % Prandtl number global new fid % new data file gas_type = 'un'; while(strncmp(gas_type,'un',2)) if(strncmp(new,'y',1)) fprintf('Available gas types are:\n'); fprintf(' hy)drogen)\n'); fprintf(' he)lium\n'); fprintf(' ai)r\n'); gas_type = input('enter gas type: ','s'); gas_type = [gas_type(1), gas_type(2)]; fprintf(fid, '%s\n', gas_type); else fscanf(fid, '%c',1); % bypass the previous newline character gas_type = fscanf(fid, '%c',2); end if(strncmp(gas_type,'hy',2)) fprintf('gas type is hydrogen\n') gama = 1.4; rgas = 4157.2; mu0 = 8.35e-6; t_suth = 84.4; elseif(strncmp(gas_type,'he',2)) fprintf('gas type is helium\n') gama = 1.67; rgas = 2078.6; mu0 = 18.85e-6; t_suth = 80.0; elseif(strncmp(gas_type,'ai',2)) fprintf('gas type is air\n') gama = 1.4; rgas = 287.0; mu0 = 17.08e-6; t_suth = 112.0; else fprintf('gas type is undefined\n') gas_type = 'un'; end end cv = rgas/(gama - 1); cp = gama*cv; t0 = 273; prandtl = 0.71; |
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Stirling Cycle Machine Analysis by
Israel
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