you may plot, but even if you couldnt plot i would like to see answers, you coul
ID: 2996093 • Letter: Y
Question
you may plot, but even if you couldnt plot i would like to see answers, you could use Matlab or EES to plot, and if you did please show me (code. results..)
A vapor compression system for an industrial freezer, must be designed to meet a refrigeration load of Qevap = 7.5 tons at Tc = -25 degree C and TH = 27 degree C. The degree of superheat of Delta T sh = 2.3 degree, degree of subcooling of Delta T sc = 2.3 degree C: and compressor isentropic efficiency of eta c = 0.80 and volumetric efficiency of eta vol= 0.77. The cost of the compressor required by the system scales with the compressor displacement rate according to: where Vdtsp in cfm. The costs of the condenser and evaporator scale with their conductances (UAcond and UAevap: respectively) according to: The conductances of the condenser and evaporator are estimated according to: The cost of the electricity required to run the refrigeration system is ec = 0.10 $/kW.hr and the system runs continuously. Determine the compressor displacement rate, condenser conductance; and evaporator conductance that minimize the overall cost of owning and operating the equipment for time = 5 years while providing the required refrigeration rate at the given conditions. Neglect the time value of money for this problem. Your solution must include plot that displays the operating cost: evaporator cost: system cost (compressor; condenser and evaporator costs) and the total cost (system and operating costs) with the condenser approach temperature Delta Tcond = 5.6 degree C is being fixed). You must find optimal total cost and explain the trend logicallyExplanation / Answer
Answer question
function [mdot, f, kW, Tdis, exitflag_m] = compressor(Qevap, Psuc, Pdis, Tsuc, hein);
p=Tchparm;p.dP_HX=1;
% initialization
options_m = optimset('LargeScale','off','Algorithm','trust-region-reflective','Display','off','TolFun',1e-10,'TolX',1e-6);
% oil fraction
tref=refpropm('t','h',200e3,'s',1e3,p.Refname); %IIR reference
funh=@(T) 4.186.*(.388+.00045.*(1.8.*T+32))./((.97386-6.91473e-4.*T)*1e3/998.5).^.5; %kJ/kg K
if Tsuc==0
[rhosuc,hsuc,ssuc]=refpropm('DHS','P',Psuc,'Q',1,p.Refname);
else
hsuc1=refpropm('H','P',Psuc,'Q',1,p.Refname);
hsuc=refpropm('H','T',Tsuc,'P',Psuc,p.Refname);
if hsuc<hsuc1
[rhosuc,hsuc,ssuc]=refpropm('DHS','P',Psuc,'Q',1,p.Refname);
else
[rhosuc,hsuc,ssuc]=refpropm('DHS','T',Tsuc,'P',Psuc,p.Refname);
end
end
[Tdis hdis rhodis]= refpropm ('THD','P',Pdis,'S',ssuc,p.Refname);
% refrigerant enthalpy at condenser outlet and assume isenthalpic expansion
if p.dP_HX==1 && hein==0
%initial hliq with 1kPa pressure drop in each tube and zero subcool and zero superheat to calc mdot guess
[Tcout hcout]= refpropm ('TH','P',Pdis-(1*p.cond.Ntot/p.cond.tube.div),'Q',0,p.Refname);
hoilcout=200e3+quadl(funh,tref-273.15,Tcout-273.15)*1e3;
hcout=p.oilcon*hoilcout+(1-p.oilcon)*hcout;
xein=refpropm('Q','P',Psuc+(1*p.evap.Ntot/p.evap.tube.div),'H',hcout,p.Refname);%r-410a
hevaprefliqin=refpropm('H','P',Psuc+(1*p.evap.Ntot/p.evap.tube.div),'Q',0,p.Refname);
hevaprefgasin=refpropm('H','P',Psuc+(1*p.evap.Ntot/p.evap.tube.div),'Q',1,p.Refname);
elseif hein==0
%initial hliq to calc mdot guess
hcout= refpropm ('H','P',Pdis,'Q',0,p.Refname);
hoilcout=200e3+quadl(funh,tref-273.15,Tcout-273.15)*1e3;
hcout=p.oilcon*hoilcout+(1-p.oilcon)*hcout;
xein=refpropm('Q','P',Psuc,'H',hcout,p.Refname);%r-410a
hevaprefliqin=refpropm('H','P',Psuc,'Q',0,p.Refname);
hevaprefgasin=refpropm('H','P',Psuc,'Q',1,p.Refname);
end
if p.oilcon==0
oilconlocal=0;
else
oilconlocal=(1-p.oilcon)/(1-(1-p.oilcon));
end
T1=refpropm('T','P',Psuc,'Q',1,p.Refname);T2=refpropm('T','P',Psuc+1,'Q',1,p.Refname);
equations=[1 T1;1 T2];values=[log(Psuc)*T1;log(Psuc+1)*T2];constants=equations alues;
A=constants(1)+182.5.*oilconlocal-724.2.*oilconlocal.^2+3868.*oilconlocal.^3-5268.9.*oilconlocal.^4;
B=constants(2)-.722.*oilconlocal+2.391.*oilconlocal.^2-13.779.*oilconlocal.^3+17.066.*oilconlocal.^4;
Tbulb=A./(log(Psuc)-B);
heout= refpropm ('H','T',Tbulb,'Q',1-p.oilcon,p.Refname);
% enthalpy of ref-oil mixture (J/kg) from oil thermodynamic property paper
hoileout=200e3+quadl(funh,tref-273.15,Tbulb-273.15)*1e3;
heout=p.oilcon*hoileout+(1-p.oilcon)*heout;
hoilsuc=200e3+quadl(funh,tref-273.15,Tsuc)*1e3;
hsuc=p.oilcon*hoilsuc+(1-p.oilcon)*hsuc;
if hein~=0
mdot=1000*Qevap/(heout-hein); % refrigerant mass flow rate in kg/sec
else
hoilein=200e3+quadl(funh,tref-273.15,MIT.Teia(i)-273.15)*1e3;
heinguess=p.oilcon*hoilein+(1-xein-p.oilcon)*hevaprefliqin+xini*hevaprefgasin;
mdot=1000*Qevap/(heout-heinguess); % refrigerant mass flow rate in kg/sec
end
if mdot<0;
mdot=0;
end
% moil = p.oilcon*mdot; % mass flow of refrigerant oil [kg/s]
vdot = mdot/rhosuc; % volumetric flow rate
Prat=Pdis/Psuc; % compression ratio
if Prat<0
display ('Prat<0');
end
% calculating power
eta_comb = p.C4 + p.C5*exp(p.C6*Prat);
% itterating discharge temperature
[y,~,~,exitflag_m] = lsqnonlin(@compressor,Tdis,Tdis,p.T_max,options_m);
if exitflag_m<=0
keyboard;
end
Tdis = y;
function result = compressor (y)
% refrigerant properties at compressor inlet
Tdis=y;
% if Tdis> 373 %100+373
% Tdis=373;
% end
[hdis rhodis]= refpropm ('HD','T',Tdis,'P',Pdis,p.Refname);
ns = log(Prat)/log(rhodis/rhosuc);
% calculating frequency
etaV = 1-p.C2*((Prat^(1/ns))-1);
f = (vdot + p.C3*(Pdis-Psuc)/1000)./(p.C1*etaV);
kW_comp = (1/eta_comb)*mdot*(ns/(ns-1))*(Psuc/rhosuc).*((Prat^((ns-1)/ns))-1); % kW
%kW_Loss = 24.0+0.0145*(kW_comp*1000); % W
kW = kW_comp;%+kW_Loss/1000; % kW
hoildis=200e3+quadl(funh,tref-273.15,Tdis)*1e3;
hdis=p.oilcon*hoildis+hdis;
Qcomp = mdot*(hdis-hsuc)/1000; % kW
% equation that needs to be satisfied
result = kW_comp-Qcomp;
end
end
% Tcpharm function
function p=Tchparm;
%% General:
p.Pamb = 101.325; % atmospheric pressure [kPa]
%% Refrigerant Specifications:
p.Refname='R410a'; % refrigerant that is used
p.Refmix1='R125';p.Refmix2='R32';p.Refmixcomp=[.5 .5];
p.airname='air';p.watername='water';p.Pamb=101.325;
p.Mref = 72.585; % molar mass for R410A [kg/kmol]
p.T_min = 142.89;%for two phase region
p.P_max = 500*6.89476; %for two phase region
p.T_max=400; %for single phase region 100+273
p.Pcr = 4.9e3; % critical pressure [kPa]
p.Ptp=30;
%% Oil Specifications:
p.oilcon = 0.01; % precentage of oil in the refrigerant [-]
%% Evaporator Parameters:
p.evap.vertical=.34;p.evap.width=.62;
p.evap.Ntot=32;p.evap.tube.div=2;
% Tube Parameters:
p.evap.tube.row=2;
p.evap.tube.pitchtransverse=20.6375e-3;
p.evap.tube.length=620e-3;
p.evap.tube.Do=6.7564e-3;
p.evap.tube.t=.8e-3;
p.evap.tube.k=400;
%%
% Fin Parameters:
p.evap.fin.t=.1016e-3;
p.evap.fin.w=25.4e-3/2;
p.evap.fin.p=1.27e-3; %18 fins per inch
p.evap.fin.k=235;
%% Condenser Parameters:
p.cond.vertical=.5048;p.cond.width=.889;
p.cond.Ntot=24;p.cond.tube.div=2;
% Tube Parameters:
p.cond.tube.Nliq=4;
p.cond.tube.row=1;
p.cond.tube.pitchtransverse=21e-3;
p.cond.tube.length=870e-3;
p.cond.tube.Do=6.5278e-3;
p.cond.tube.t=.8e-3;
p.cond.tube.k=400;
%%
% Fin Parameters:
p.cond.fin.t=7.62e-5;
p.cond.fin.w=21.96e-3;
p.cond.fin.p=1.41e-3; %20 fins per inch
p.cond.fin.k=235;
%% Chiller Parameters:
p.chiller.plates = 14; % number of plates
p.chiller.plate_length = 0.415; %[m] chiller lenght
p.chiller.plate_width = 0.0858; %[m] chiller width
p.chiller.plate_depth = 0.0425; %[m] chiller depth
p.chiller.plate_thick=.5e-3; %[m]
p.chiller.plate.k=16; %[W/mK]
p.chiller.developed_length= 6.5*2.1*1e-3; %[m] taken in 2.1 finite steps
p.chiller.protracted_length = 12.3*1e-3; %[m] taken in 2.1 finite steps
p.chiller.channel_thickness=2.2352e-3;
p.chiller.corrugation_pitch=6.8e-3;
p.chiller.chevron_angle = 60;
p.chiller.dia_water = 26e-3; %[m] water connection diameter
p.chiller.dia_ref = 26e-3; %[m] refrigerant connection diameter
%% Compressor Parameters:
% Tea's Model Constants:
p.C1=9.20000000000000e-06;p.C2=0.11556185;p.C3=1.52444E-05;
p.C4=-0.090012328;p.C5=1.053942728;p.C6=-0.159224192;
%% Outdoor Fan Data:
%MIT
%cfm= 0.6487*rpm^1.096
%3phpower=1.958e-7*flow^2.703
%MI
%cfm=.739*rpm^1.084
%3phpower=5.093e-9*flow^3.27
%W=c1*x^c2
p.cfanC1MI=383.126;p.cfanC2MI=3.27;
p.cfanC1MIT=191.55;p.cfanC2MIT=2.703;
p.cfanC1=383.126;p.cfanC2=3.27;
%% Fan and Pump Power Exponents
p.cfanC1=191.8;p.cfanC2=2.703;
p.efanC1=431;p.efanC2=1.792;
%p.efanC1= 2.758e+006;p.efanC2= 1.493;p.efanC3=18.63; %for grundfos pump alpha2l-50 with CP2
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