/[ascend]/trunk/models/johnpye/radialheatloss.a4c
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Tue May 16 08:27:05 2006 UTC (18 years, 9 months ago) by johnpye
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Adding a simple model for radial heat loss, eg from an insulated pipe. Under development.
1 johnpye 611 (* ASCEND model library
2     Copyright (c) 2006 Carnegie Mellon University
3    
4     This program is free software; you can redistribute it
5     and/or modify it under the terms of the GNU General Public
6     License as published by the Free Software Foundation; either
7     version 2 of the License, or (at your option) any later
8     version.
9    
10     This program is distributed in the hope that it will be
11     useful, but WITHOUT ANY WARRANTY; without even the implied
12     warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
13     PURPOSE. See the GNU General Public License for more
14     details.
15    
16     You should have received a copy of the GNU General Public
17     License along with this program; if not, write to the Free
18     Software Foundation, Inc., 59 Temple Place, Suite 330,
19     Boston, MA 02111-1307 USA
20     *)(**
21     This is a simple model for computing the
22     steady-state temperature and heat loss profile
23     of a multi-layered pipe-plus-insulation
24    
25     by John Pye
26     *)
27    
28     REQUIRE "atoms.a4l";
29     REQUIRE "johnpye/thermo_types.a4c";
30    
31     MODEL radial_loss;
32     D_1 IS_A distance;
33     D_2 IS_A distance;
34     q IS_A energy_rate;
35     L IS_A distance;
36     T_1, T_2 IS_A temperature;
37     METHODS
38     METHOD specify;
39     FIX D_1, D_2;
40     END specify;
41     END radial_loss;
42    
43     (*
44     Wall conduction
45     *)
46     MODEL wall_conduction REFINES radial_loss;
47     k IS_A thermal_conductivity;
48    
49     q = 2 * 1{PI} * L * k *(T_1 - T_2) / ln(D_2/D_1);
50    
51     END wall_conduction;
52    
53     (*
54     Convection boundary
55     *)
56     MODEL convection_boundary REFINES radial_loss;
57     h IS_A heat_transfer_coefficient;
58     D_1, D_2 ARE_THE_SAME;
59    
60     q = h * 1{PI} * D_1 * (T_1 - T_2);
61    
62     END convection_boundary;
63    
64     (*
65     A sequence of radial losses in series
66     *)
67     MODEL radial_losses(
68     n WILL_BE integer;
69     ) REFINES radial_loss;
70    
71     loss[1..n] IS_A radial_loss;
72    
73     (* all the same length *)
74     L, loss[1..n].L ARE_THE_SAME;
75    
76     (* the ID of the whole lot equals the ID for the first element *)
77     D_1, loss[1].D_1 ARE_THE_SAME;
78    
79     (* the OD of the whole lot equals the OD of the last element *)
80     D_2, loss[n].D_2 ARE_THE_SAME;
81    
82     FOR i IN [1..n] CREATE
83     (* layers are touching *)
84     loss[i].D_1, loss[i-1].D_2 ARE_THE_SAME;
85     (* heat rate is uniform *)
86     loss[i].q,loss[i-1].q ARE_THE_SAME;
87     END FOR;
88    
89     END radial_losses;
90    
91     (*
92     Sample model: a stainless steel pipe
93     with lagging (aka insulation) and a thin steel
94     sheel.
95     *)
96     MODEL test_lagged_pipe REFINES radial_losses(
97     n IS_A integer_constant;
98     )
99     n:=5;
100    
101     loss[1] IS_A convection_boundary;
102     loss[2] IS_A wall_conduction;
103     loss[3] IS_A wall_conduction;
104     loss[4] IS_A wall_conduction;
105     loss[5] IS_A convection_boundary;
106    
107     METHODS
108     METHOD specify;
109     FIX loss[1].h;
110     FIX loss[2..4].k;
111     FIX loss[5].h;
112    
113     FIX loss[1,3,5].D_1;
114     END specify;
115    
116     METHOD values;
117     loss[1].h := 1000 {W/m^2/K};
118     loss[2].k := 40 {W/m/K}; (* 'alloy steel', Ashby & Jones, Eng Matls 2, p.11 *)
119     loss[3].k := 0.05 {W/m/K}; (* Masud's figure for lagging *)
120     loss[4].k := 240 {W/m/K}; (* aluminium, Ashby & Jones, Eng Matls 2, p.11 *)
121     loss[5].h := 50 {W/m^2/K};
122    
123     loss[1].D_1 := 0.05 {m}; (* pipe interior *)
124     loss[1].D_2 := 0.07 {m}; (* pipe exterior *)
125     loss[4].D_1 := 0.17 {m}; (* cover interior *)
126     loss[4].D_2 := 0.19 {m}; (* cover exterior *)
127     END values;
128     END test_lagged_pipe;

john.pye@anu.edu.au
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