Question

Design a refrigerator working on propane ammonia and R407C refrigerant and producing -20K, -10K and O K temperature during steady state operation....

carryout experimental validation using appropriate software.

write energy and exergy equation in Fortran 77 only...
plot graph in scilab....

Answer 1

"!This program calculates the two-dimensional steady-state temperature distribution in a square plate. Two of the four edges are at 100°C, one is maintained at 0°C and one is insulated. The solution illustrates the use of 2-dimensional arrays and contour and 3-D plots."

"Notice that it is not necessary for the user to program any iterative procedures to solve the equations.

View the plot window to see a contour plot of the calculated results.
"

N=25 "Number of nodes in the X and Y directions."

"Energy balance on interior nodes. Interior nodes run from 1 to N."
duplicate i=1,N
   duplicate j=1,n
       T[i,j]=(T[i+1,j]+T[i-1,j]+T[i,j+1]+T[i,j-1])/4
   end
end

"Boundary conditions. Boundary nodes are 0 and N+1."
duplicate i=0,N+1
   T[i,0]=100 "Left hand side set to 100°C."
   T[i,N+1]=T[i,N] "Insulated right hand side - no temperature gradient."
end
duplicate j=1,N
   T[0,j]=100 "Bottom surface at 100°C."
   T[N+1,j]=0 "Top surface at 0°C."
end

$TabWidth 0.5 cm

"!This program demonstrates the use of the Integral functions to solve second order equations. "

"Here EES is used to calculate the velocity and position of a freely falling sphere, subject to aerodynamic drag. The unit system is set to English. The graph is set to automatic update - change v_o to -50 to see the impact of an initial upward velocity.

Note how the Integral function displays on the Formatted Equations Window."

D=0.25 [ft]
m=1.0 [lb_m]    "mass of sphere"
v_o=0 [ft/s]    "initial velocity."
z_o=0 [ft]     "initial position"
time=5 [s]   "time period for analysis"
g=32.17 [ft/s^2]    "gravitational acceleration"

F=m*g*Convert(lbm-ft/s^2,lbf)         "Newton's Law"
m*a*Convert(lbm-ft/s^2,lbf)=F-F_d        "force balance"
Area=pi*D^2/4           "frontal area of sphere"
F_d=Area*C_d*(1/2*rho*v^2)*Convert(lbm-ft/s^2,lbf)    "definition of drag coefficient"

"Find Reynolds number"
mu=viscosity(air, T=70)*Convert(1/hr,1/s)
rho=density(Air,T=70,P=14.7)
Re=rho*abs(v)*D/mu

"Find drag coefficient from the Reynolds number. The Lookup table contains ln(Re) and ln(C_d). The max function is used to prevent attempting to find the log of zero (i.e., when the velocity is zero use a small value of Re)"
C_d=exp(interpolate1( 'LnRe', 'LnCd', LnRe=Ln(max(.01, Re))))

"As a test of the need for tthe variable drag coefficient, set C_d to a constant value, say C_d=0.4. Turn off automatic update on the plots (click on the plot window) and overlay the new plots, using the left scale."
{C_d=0.4}

"Use EES integral function to determine velocity and position given the acceleration."
v=v_o+integral(a,t,0,time)   "velocity after 5 seconds"
z=z_o+integral(v,t,0,time)   "vertical position after 5 seconds"

"The following directive instructs EES to store values of v (velocity), z (elevation) and C_d (drag coefficient) as a function of t (time) at increments of 0.2 sec.
"
$integraltable t:0.2, v,z, C_d
$tabstops 1 in