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Revision 2720 - (show annotations) (download) (as text)
Thu Dec 5 06:26:27 2013 UTC (10 years, 7 months ago) by jpye
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fix env vars before running tests
1 REQUIRE "johnpye/datareader/testairprops.a4c";
2
3 (*
4 Model to calculation natural convection heat loss from a vertical wall.
5 The model makes use of interpolated air properties from Holman 10e table
6 A-5 for conductivity, viscosity, and specific heat capacity.
7 *)
8 MODEL wallfreeconvection;
9
10 T_w, T_amb, T_f IS_A temperature;
11
12 T_f = 0.5*(T_w + T_amb);
13
14 air IS_A airprops(T_f);
15
16 Gr, Pr, Ra, Nu IS_A factor;
17
18 L IS_A distance;
19
20 nu IS_A kinematic_viscosity;
21 nu = air.mu / air.rho;
22
23 Gr = 9.81{m/s^2} * (1./T_f) * (T_w - T_amb) * L^3 / nu^2;
24
25 Pr = air.cp * air.mu / air.k;
26
27 Ra = Gr * Pr;
28
29 (* Churchill & Chu correlation, as per Holman 10e, p 335, for Ra<1e9 *)
30 (*Nu = 0.68 + 0.670 * Ra^0.25 / (1 + (0.493/Pr)^(9./16))^(4./9);*)
31
32 (* Churchill & Chu correlation, as per Holman 10e, p 335, for 0.1<Ra<1e12 *)
33 sqrt(Nu) = 0.825 + (0.387*Ra^(1./6)) / (1 + (0.492/Pr)^(9./16))^(8./27);
34
35 h IS_A heat_transfer_coefficient;
36 Nu = h*L / air.k;
37
38 Qdd IS_A energy_flux;
39 Qdd = h * (T_w - T_amb);
40
41 METHODS
42 METHOD on_load;
43 FIX L := 2.4 {m};
44 FIX T_w := 96{K} + 273.15{K};
45 FIX T_amb := 35{K} + 273.15{K};
46 END on_load;
47 END wallfreeconvection;

john.pye@anu.edu.au
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