models/johnpye/absorber.a4c

REQUIRE "johnpye/iapws95.a4c";
REQUIRE "johnpye/iapws_sat_curves.a4c";

MODEL absorber;
	(* assumptions: 
		outlet is saturated steam
		inlet is saturated water at the specified pressure
		no pressure drop
		no temperature change
		all Q is absorbed by water
		steam generation is constant along length as mass rate, so x rises linearly.
	*)
	S_out IS_A iapws95_2phase; (* outlet steam state *)
	sat IS_A iapws_sat_density;
	T ALIASES S_out.T;
	T,sat.T ARE_THE_SAME;
	rho_gas ALIASES S_out.rho;
	rho_gas, sat.rhog ARE_THE_SAME;

	p ALIASES S_out.p;

	mdot_water_in IS_A mass_rate;
	mdot_water_out IS_A mass_rate;
	mdot_gas_out IS_A mass_rate;
	Vdot_gas_out IS_A volume_rate;

	m_water IS_A mass;
	m_gas IS_A mass;

	Q IS_A energy_rate; (* heat absorbed *)

	(* assume saturated water at inlet, so any heat added immediately creates some steam *)
	Hdot_in IS_A energy_rate;
	Hdot_out IS_A energy_rate;
	h_water IS_A specific_enthalpy;
	z01: h_water = 400 {kJ/kg} + p / (1000 {kg/m^3});

	z02: Hdot_in = mdot_water_in * h_water;
	z03: Hdot_out = mdot_water_out * h_water + mdot_gas_out * S_out.h;

	(* 1st law thermo *)
	z04: Q = Hdot_out - Hdot_in;

	(* mass conservation *)
	z05: mdot_water_in = mdot_water_out + mdot_gas_out;
 
	x_exit IS_A fraction;
	z06: x_exit * mdot_water_in = mdot_gas_out;

	(* assume that steam evolves linearly along length, so average x allow mass of water to be calculated *)
	x IS_A fraction;
	z07: x = (0 + x_exit)/2;
	
	(* assuming a slip-ratio of 1, we can get the average void ratio, eq 2.13 from Behnia *)
	alpha IS_A fraction;
	z08: alpha * S_out.rho * (1-x) = 1000{kg/m^3} * x * (1-alpha);

	z09: m_water = 1000{kg/m^3} * (1-alpha)*V_total;
	z10: m_gas = S_out.rho * alpha*V_total;

	z11: Vdot_gas_out = mdot_gas_out / rho_gas;
	V_total IS_A volume;
	
METHODS
METHOD default_self;
	RUN reset;
	RUN values;
END default_self;
METHOD specify;
	FIX V_total, mdot_water_in, Q, p;
END specify;
METHOD values;
	V_total := 300{m} * 16 * 1{PI}*( 40{mm} )^2;
	mdot_water_in := 0.4 {kg/s};
	Q := 1000 {W/m^2} * 27(*concentration*) * 500{mm} * 60{m};
	p := 5 {bar};
END values;

END absorber;
1	johnpye	265	REQUIRE "johnpye/iapws95.a4c";
2	johnpye	217	REQUIRE "johnpye/iapws_sat_curves.a4c";
3
4			MODEL absorber;
5			(* assumptions:
6			outlet is saturated steam
7			inlet is saturated water at the specified pressure
8			no pressure drop
9			no temperature change
10			all Q is absorbed by water
11			steam generation is constant along length as mass rate, so x rises linearly.
12			*)
13	johnpye	265	S_out IS_A iapws95_2phase; (* outlet steam state *)
14	johnpye	217	sat IS_A iapws_sat_density;
15			T ALIASES S_out.T;
16			T,sat.T ARE_THE_SAME;
17			rho_gas ALIASES S_out.rho;
18			rho_gas, sat.rhog ARE_THE_SAME;
19
20			p ALIASES S_out.p;
21
22			mdot_water_in IS_A mass_rate;
23			mdot_water_out IS_A mass_rate;
24			mdot_gas_out IS_A mass_rate;
25			Vdot_gas_out IS_A volume_rate;
26
27			m_water IS_A mass;
28			m_gas IS_A mass;
29
30			Q IS_A energy_rate; (* heat absorbed *)
31
32			(* assume saturated water at inlet, so any heat added immediately creates some steam *)
33			Hdot_in IS_A energy_rate;
34			Hdot_out IS_A energy_rate;
35			h_water IS_A specific_enthalpy;
36			z01: h_water = 400 {kJ/kg} + p / (1000 {kg/m^3});
37
38			z02: Hdot_in = mdot_water_in * h_water;
39			z03: Hdot_out = mdot_water_out * h_water + mdot_gas_out * S_out.h;
40
41			(* 1st law thermo *)
42			z04: Q = Hdot_out - Hdot_in;
43
44			(* mass conservation *)
45			z05: mdot_water_in = mdot_water_out + mdot_gas_out;
46
47			x_exit IS_A fraction;
48			z06: x_exit * mdot_water_in = mdot_gas_out;
49
50			(* assume that steam evolves linearly along length, so average x allow mass of water to be calculated *)
51			x IS_A fraction;
52			z07: x = (0 + x_exit)/2;
53
54			(* assuming a slip-ratio of 1, we can get the average void ratio, eq 2.13 from Behnia *)
55			alpha IS_A fraction;
56			z08: alpha * S_out.rho * (1-x) = 1000{kg/m^3} * x * (1-alpha);
57
58			z09: m_water = 1000{kg/m^3} * (1-alpha)*V_total;
59			z10: m_gas = S_out.rho * alpha*V_total;
60
61			z11: Vdot_gas_out = mdot_gas_out / rho_gas;
62			V_total IS_A volume;
63
64			METHODS
65			METHOD default_self;
66			RUN reset;
67			RUN values;
68			END default_self;
69			METHOD specify;
70	johnpye	218	FIX V_total, mdot_water_in, Q, p;
71	johnpye	217	END specify;
72			METHOD values;
73			V_total := 300{m} * 16 * 1{PI}*( 40{mm} )^2;
74			mdot_water_in := 0.4 {kg/s};
75			Q := 1000 {W/m^2} * 27(concentration) * 500{mm} * 60{m};
76			p := 5 {bar};
77			END values;
78
79			END absorber;