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(* ASCEND model library |
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Copyright (c) 2006 Carnegie Mellon University |
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This program is free software; you can redistribute it |
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and/or modify it under the terms of the GNU General Public |
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License as published by the Free Software Foundation; either |
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version 2 of the License, or (at your option) any later |
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version. |
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|
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This program is distributed in the hope that it will be |
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useful, but WITHOUT ANY WARRANTY; without even the implied |
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warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR |
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PURPOSE. See the GNU General Public License for more |
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details. |
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|
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You should have received a copy of the GNU General Public |
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License along with this program; if not, write to the Free |
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Software Foundation, Inc., 59 Temple Place, Suite 330, |
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Boston, MA 02111-1307 USA |
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*)(** |
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This is a simple model for computing the |
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steady-state temperature and heat loss profile |
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of a multi-layered pipe-plus-insulation |
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|
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by John Pye |
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*) |
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|
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REQUIRE "atoms.a4l"; |
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REQUIRE "johnpye/thermo_types.a4c"; |
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|
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MODEL radial_loss; |
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D_1 IS_A distance; |
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D_2 IS_A distance; |
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q IS_A energy_rate; |
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L IS_A distance; |
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T_1, T_2 IS_A temperature; |
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METHODS |
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METHOD specify; |
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FIX D_1, D_2; |
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END specify; |
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END radial_loss; |
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|
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(* |
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Wall conduction |
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*) |
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MODEL wall_conduction REFINES radial_loss; |
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k IS_A thermal_conductivity; |
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|
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q = 2 * 1{PI} * L * k *(T_1 - T_2) / ln(D_2/D_1); |
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|
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END wall_conduction; |
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|
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(* |
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Convection boundary |
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*) |
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MODEL convection_boundary REFINES radial_loss; |
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h IS_A heat_transfer_coefficient; |
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D_1, D_2 ARE_THE_SAME; |
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|
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q = h * 1{PI} * D_1 * (T_1 - T_2); |
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|
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END convection_boundary; |
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|
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MODEL pipe_test REFINES radial_loss; |
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n IS_A integer_constant; |
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n:==5; |
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|
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loss[1..5] IS_A radial_loss; |
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|
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loss[1] IS_REFINED_TO convection_boundary; |
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loss[2] IS_REFINED_TO wall_conduction; |
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loss[3] IS_REFINED_TO wall_conduction; |
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loss[4] IS_REFINED_TO wall_conduction; |
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loss[5] IS_REFINED_TO convection_boundary; |
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|
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L, loss[1..5].L ARE_THE_SAME; |
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|
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FOR i IN [2..n] CREATE |
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(* layers are touching *) |
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loss[i].D_1, loss[i-1].D_2 ARE_THE_SAME; |
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(* steady state: heat rate is uniform *) |
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loss[i].q,loss[i-1].q ARE_THE_SAME; |
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|
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loss[i].T_1, loss[i-1].T_2 ARE_THE_SAME; |
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END FOR; |
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loss[i].D_1, D_1 ARE_THE_SAME; |
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loss[n].D_2, D_2 ARE_THE_SAME; |
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loss[i].T_1, T_1 ARE_THE_SAME; |
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loss[i].T_2, T_2 ARE_THE_SAME; |
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loss[i].q, q ARE_THE_SAME; |
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METHODS |
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METHOD default_self; |
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RUN reset; RUN values; |
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END default_self; |
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|
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METHOD specify; |
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FIX loss[1].h; |
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FIX loss[2..4].k; |
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FIX loss[5].h; |
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FIX loss[2].D_1, loss[2].D_2; |
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FIX loss[4].D_1, loss[4].D_2; |
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END specify; |
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METHOD values; |
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L = 1 {m}; |
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loss[1].h := 1000 {W/m^2/K}; |
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loss[2].k := 40 {W/m/K}; (* 'alloy steel', Ashby & Jones, Eng Matls 2, p.11 *) |
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loss[3].k := 0.05 {W/m/K}; (* Masud's figure for lagging *) |
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loss[4].k := 240 {W/m/K}; (* aluminium, Ashby & Jones, Eng Matls 2, p.11 *) |
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loss[5].h := 50 {W/m^2/K}; |
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loss[1].D_1 := 0.05 {m}; (* pipe interior *) |
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loss[1].D_2 := 0.07 {m}; (* pipe exterior *) |
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loss[4].D_1 := 0.17 {m}; (* cover interior *) |
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loss[4].D_2 := 0.19 {m}; (* cover exterior *) |
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END values; |
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END pipe_test; |
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