| 1 |
REQUIRE "johnpye/ideal_steam.a4c"; |
| 2 |
REQUIRE "johnpye/iapws_sat_curves.a4c"; |
| 3 |
REQUIRE "johnpye/iapws95.a4c"; |
| 4 |
|
| 5 |
MODEL condenser_lmtd( |
| 6 |
S_in WILL_BE thermo_state; |
| 7 |
S_out WILL_BE thermo_state; |
| 8 |
); |
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T_h1 ALIASES S_in.T; |
| 10 |
T_h2 ALIASES S_out.T; |
| 11 |
h_h1 ALIASES S_in.h; |
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h_h2 ALIASES S_out.h; |
| 13 |
|
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mdot_in IS_A mass_rate; |
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|
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T_c1 IS_A temperature; |
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T_c2 IS_A temperature; |
| 18 |
|
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T_c_in ALIASES T_c2; |
| 20 |
T_c_out ALIASES T_c1; |
| 21 |
|
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|
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LMTD IS_A delta_temperature; |
| 24 |
|
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DT_1, DT_2 IS_A delta_temperature; |
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|
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DT_1 = T_h1 - T_c1; |
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DT_2 = T_h2 - T_c2; |
| 29 |
|
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lmtd: LMTD = (DT_2 - DT_1) / ln(DT_2/DT_1); |
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|
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UA IS_A ua_value; |
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q IS_A energy_rate; |
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|
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q = UA * LMTD; |
| 36 |
|
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q = mdot_in * (h_h1 - h_h2); |
| 38 |
|
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S_out.p = S_in.p; |
| 40 |
|
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METHODS |
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METHOD specify; |
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FIX UA; |
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FIX T_c_in; |
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FIX mdot_in; |
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END specify; |
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METHOD values; |
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UA := 1000 {W/m^2/K} * 4 {m} * 900 * 2*3.1415926* (0.01 {m})/2; |
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T_c_in := 273.15{K} + 20 {K}; |
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mdot_in := 1 {kg/s}; |
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(* free values *) |
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T_h2 := T_h1 - 20{K}; |
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h_h2 := h_h1 - 4.2{kJ/kg/K}*20{K}; |
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END values; |
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METHOD bound_self; |
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DT_1.lower_bound := 0{K}; |
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DT_2.lower_bound := 0{K}; |
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q.lower_bound := 0{W}; |
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T_h2.upper_bound := T_h1; |
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T_h2.lower_bound := T_c_out; |
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h_h2.upper_bound := h_h1; |
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END bound_self; |
| 63 |
END condenser_lmtd; |
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|
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(*--------------------------*) |
| 66 |
|
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(* test model for the above *) |
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MODEL condenser_lmtd_test; |
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S1 IS_A iapws95_1phase; |
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S2 IS_A iapws95_1phase; |
| 71 |
|
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T_in ALIASES S1.T; |
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p_in ALIASES S1.p; |
| 74 |
|
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C IS_A condenser_lmtd(S1,S2); |
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|
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q ALIASES C.q; |
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|
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METHODS |
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METHOD default_self; |
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RUN reset; RUN values; RUN bound_self; |
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END default_self; |
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METHOD specify; |
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RUN C.specify; |
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FIX T_in; |
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FIX p_in; |
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FIX C.T_c_out; |
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END specify; |
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METHOD values; |
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RUN C.values; |
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T_in := 273.15{K} + 280 {K}; |
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p_in := 1{bar}; |
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q := 4.2{kJ/s}; |
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C.T_c_out := 273.15{K} + 25 {K}; |
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END values; |
| 96 |
METHOD bound_self; |
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RUN C.bound_self; |
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END bound_self; |
| 99 |
END condenser_lmtd_test; |
| 100 |
|
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|
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(*--------------------------*) |
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MODEL condenser_lmtd_sat( |
| 104 |
S_in WILL_BE thermo_state; |
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S_out WILL_BE thermo_state; |
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); |
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T_in ALIASES S_in.T; |
| 108 |
|
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mdot_in IS_A mass_rate; |
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mdot_out ALIASES mdot_in; |
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|
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T_c1 IS_A temperature; (* cold inlet *) |
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T_c2 IS_A temperature; (* cold outlet *) |
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|
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LMTD_fg IS_A delta_temperature; |
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|
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DT_c_fg, DT_1, DT_2 IS_A delta_temperature; |
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|
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DT_c_fg = T_c2 - T_c1; |
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DT_1 = T_in - T_c1; |
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DT_2 = T_in - T_c2; |
| 122 |
|
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lmtd: LMTD_fg = (DT_c_fg) / ln(DT_1/DT_2); |
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(* lmtd: LMTD_fg * -ln((T_in - T_c1)/(T_in - T_c2)) = (T_c2 - T_c1); *) |
| 125 |
|
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UA_fg IS_A ua_value; |
| 127 |
q_fg IS_A energy_rate; |
| 128 |
|
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q_fg = UA_fg * LMTD_fg; |
| 130 |
|
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(* condensation point *) |
| 132 |
Sf ALIASES S_out; |
| 133 |
|
| 134 |
sat IS_A iapws_sat_density; |
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sat.rhof = Sf.rho; |
| 136 |
sat.T = Sf.T; |
| 137 |
|
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S_in.T = Sf.T; |
| 139 |
|
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q_fg = mdot_in * (S_in.h - Sf.h); |
| 141 |
METHODS |
| 142 |
METHOD specify; |
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FIX UA_fg; |
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FIX T_c1; |
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FIX mdot_in; |
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END specify; |
| 147 |
METHOD values; |
| 148 |
UA_fg := 4000 {W/m^2/K} * 4 {m} * 900 * 2*3.1415926* (0.01 {m})/2; |
| 149 |
T_c1 := 273.15{K} + 200 {K}; |
| 150 |
mdot_in := 10 {kg/s}; |
| 151 |
(* free values *) |
| 152 |
T_c2 := 273.15{K} + 240 {K}; |
| 153 |
END values; |
| 154 |
METHOD bound_self; |
| 155 |
Sf.tau.lower_bound := 1; |
| 156 |
DT_c_fg.lower_bound := 0{K}; |
| 157 |
DT_1.lower_bound := 0{K}; |
| 158 |
DT_2.lower_bound := 0{K}; |
| 159 |
Sf.rho.lower_bound := Sf.rhoc; |
| 160 |
END bound_self; |
| 161 |
END condenser_lmtd_sat; |
| 162 |
|
| 163 |
(*------------------------------*) |
| 164 |
|
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MODEL condenser_lmtd_sat_test; |
| 166 |
Sg IS_A iapws95_1phase; |
| 167 |
Sf IS_A iapws95_1phase; |
| 168 |
|
| 169 |
sat IS_A iapws_sat_density; |
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sat.rhog, Sg.rho ARE_THE_SAME; |
| 171 |
sat.T, Sg.T ARE_THE_SAME; |
| 172 |
T_in ALIASES Sg.T; |
| 173 |
|
| 174 |
C IS_A condenser_lmtd_sat(Sg,Sf); |
| 175 |
|
| 176 |
METHODS |
| 177 |
METHOD default_self; |
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RUN reset; RUN values; RUN bound_self; |
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END default_self; |
| 180 |
METHOD specify; |
| 181 |
RUN C.specify; |
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FIX T_in; |
| 183 |
END specify; |
| 184 |
METHOD values; |
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RUN C.values; |
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T_in := 273.15{K} + 280 {K}; |
| 187 |
END values; |
| 188 |
METHOD bound_self; |
| 189 |
RUN C.bound_self; |
| 190 |
END bound_self; |
| 191 |
METHOD self_test; |
| 192 |
ASSERT (C.q_fg - 15430{kW}) < 1{kW}; |
| 193 |
END self_test; |
| 194 |
END condenser_lmtd_sat_test; |
| 195 |
|
| 196 |
(*-----------------------------*) |
| 197 |
|
| 198 |
MODEL condenser; |
| 199 |
(* assumptions: |
| 200 |
inlet is ideal-gas steam at specified temperature and pressure. |
| 201 |
output is water of fixed enthalpy. |
| 202 |
whatever energy is required to be taken away to acheive that is what will be taken away. |
| 203 |
|
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we don't need to enforce saturation inlet conditions. we will just query the enthalpy for the ideal-gas steam |
| 205 |
and that's it. |
| 206 |
*) |
| 207 |
S_in IS_A ideal_steam; |
| 208 |
|
| 209 |
mdot_gas_in IS_A mass_rate; |
| 210 |
mdot_water_out IS_A mass_rate; |
| 211 |
Q IS_A energy_rate; (* heat taken away by condenser *) |
| 212 |
|
| 213 |
h_in ALIASES S_in.h; |
| 214 |
p_in ALIASES S_in.p; |
| 215 |
T_in ALIASES S_in.T; |
| 216 |
|
| 217 |
(* |
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h2 will be the enthalpy of the condensed water. because we are |
| 219 |
ignoring pressure effects, we have to assume a constant fixed |
| 220 |
value for the enthalpy of water at x=0. |
| 221 |
*) |
| 222 |
h_out IS_A specific_enthalpy; |
| 223 |
|
| 224 |
Q = mdot_gas_in * h_in - mdot_water_out * h_out; |
| 225 |
mdot_water_out = mdot_gas_in; |
| 226 |
|
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(* |
| 228 |
we will assume there is NO water in the condenser for now; the |
| 229 |
surge tank will play the role of the mass holdup in this case. |
| 230 |
*) |
| 231 |
METHODS |
| 232 |
METHOD default_self; |
| 233 |
RUN reset; |
| 234 |
RUN values; |
| 235 |
END default_self; |
| 236 |
METHOD specify; |
| 237 |
FIX mdot_gas_in; |
| 238 |
FIX S_in.p, S_in.T; |
| 239 |
FIX h_out; |
| 240 |
END specify; |
| 241 |
METHOD values; |
| 242 |
mdot_gas_in := 1 {kg/s}; |
| 243 |
S_in.p := 5 {bar}; |
| 244 |
S_in.T := 473.15 {K}; |
| 245 |
h_out := 400{kJ/kg}; |
| 246 |
END values; |
| 247 |
END condenser; |
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