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@nakawimi
@nakawimi 2 күн бұрын
During the exam i wont have the chance to use EES, how can i solve the problem manually? Thank you for the video.
@SuemonKwok
@SuemonKwok 2 күн бұрын
150 kPa and 200 ℃ is superheated but no exact superheated table you need to linear interpolate on table A-6 (0.10 MPa at 200 ℃ where this is the minimum) and (0.20 MPa at 200 ℃ where this is the maximum) it's not exact but it's an approximation of what the value is
@nakawimi
@nakawimi 2 күн бұрын
@@SuemonKwok thank you!
@iloveyouso-ty1ps
@iloveyouso-ty1ps 5 күн бұрын
thanks for everything, you really save my life
@SuemonKwok
@SuemonKwok 4 күн бұрын
Thanks for watching
@nakawimi
@nakawimi 9 күн бұрын
if i had these videos the first time i took the class, i would be graduated by now. great work thank you.
@SuemonKwok
@SuemonKwok 9 күн бұрын
Thanks for watching, as a former struggling mechanical engineering student who eventually graduated. I understand the struggle. The playlist and series has evolved initially it was aimed at students who knew what they were doing and wanted to revise. As more questions came in from viewers the videos became step by step tutorials
@Shankar-lz7zs
@Shankar-lz7zs 12 күн бұрын
Sir cfa help to get into finance job in NZ
@mqinamolebogeng3287
@mqinamolebogeng3287 13 күн бұрын
Thank you👍🏽
@SuemonKwok
@SuemonKwok 13 күн бұрын
Thanks for watching
@SuemonKwok
@SuemonKwok 15 күн бұрын
Correction: Not 120℉ and 140 ℉ linear interpolation The final state is superheated vapor and the internal energy at this state should be obtained by interpolation using 50 psia and 60 psia mini tables (100°F line) in Table A-13E.
@kevinnarine1106
@kevinnarine1106 15 күн бұрын
My question is, how did you know where in the table to interpolate? I mean, how did you know to interpolate the values at 60 psia between 120 and 140 degrees Fahrenheit?
@SuemonKwok
@SuemonKwok 15 күн бұрын
For this question EES was used. How you did identify a mistake. I'll post in the in the pinned comment
@SuemonKwok
@SuemonKwok 17 күн бұрын
Disclaimer the code is has been uploaded to anti cheat software such as Turnitin. Use it to check your answer. P2=1200 [kPa] T2=700 [C] T3=1200 [C] P3=P2 "1" v2=volume(steam_iapws, P=P2, T=T2) v1=v2 P1=pressure(steam_iapws, x=1, v=v1) "2" v3=volume(steam_iapws, P=P3, T=T3) w_b=P2*(v3-v2) "3" u1=intenergy(steam_iapws, x=1, v=v1) u3=intenergy(steam_iapws, P=P3, T=T3) q=u3-u1+w_b
@SuemonKwok
@SuemonKwok 17 күн бұрын
Disclaimer the code is has been uploaded to anti cheat software such as Turnitin. Use it to check your answer. R=0.3 [kJ/kg-K] c_v=0.7 [kJ/kg-K] DELTAT=100 [K] "(1)" c_p=R+c_v DELTAh=c_p*DELTAT "(2)" DELTAu=c_v*DELTAT "(5)" PV=R*DELTAT
@SuemonKwok
@SuemonKwok 17 күн бұрын
Disclaimer the code is has been uploaded to anti cheat software such as Turnitin. Use it to check your answer. m_ball=5 [kg] T=100 [C] T1=25 [C] T2=100 [C] cp=1.8 [kJ/kg-C] Q=m_ball*cp*(T2-T1) Q=m_steam*h_fg h_f=ENTHALPY(Steam_IAPWS, x=0,T=T) h_g=ENTHALPY(Steam_IAPWS, x=1,T=T) h_fg=h_g-h_f "Some Wrong Solutions with Common Mistakes:" Q=W1m_steam*h_g "Using h_g" Q=W2m_steam*cp*(T2-T1) "Using m*c*DeltaT = Q for water" Q=W3m_steam*h_f "Using h_f"
@SuemonKwok
@SuemonKwok 17 күн бұрын
Disclaimer the code is has been uploaded to anti cheat software such as Turnitin. Use it to check your answer. m=6*0.355 [kg] T1=18 [C] T2=3 [C] c=4.18 [kJ/kg-K] DELTAT=T2-T1 "Applying energy balance E_in-E_out=dE_system and noting that dU_system=m*c*DELTAT gives" -Q_out=m*c*DELTAT "Some Wrong Solutions with Common Mistakes:" -W1_Qout=m*c*DELTAT/6 "Using one can only" -W2_Qout=m*c*(T1+T2) "Adding temperatures instead of subtracting" -W3_Qout=m*1.0*DELTAT "Using specific heat of air or forgetting specific heat"
@SuemonKwok
@SuemonKwok 17 күн бұрын
Disclaimer the code is has been uploaded to anti cheat software such as Turnitin. Use it to check your answer. m=0.18 [kg] T1=17 [C] T2=5 [C] c=3.65 [kJ/kg-K] -Q_out = dU_system "from energy balance E_in-E_out=dE_system" dU_system=m*c*(T2-T1) "Some Wrong Solutions with Common Mistakes:" -W1_Qout =c*(T2-T1) "Not using mass" -W2_Qout =m*c*(T2+T1) "adding temperatures
@SuemonKwok
@SuemonKwok 17 күн бұрын
Disclaimer the code is has been uploaded to anti cheat software such as Turnitin. Use it to check your answer. m=0.1 [kg] T1=5 [C] T2=95 [C] c=3.32 [kJ/kg-K] E_in = dU_system "from energy balance E_in-E_out=dE_system" dU_system=m*c*(T2-T1) "Some Wrong Solutions with Common Mistakes:" W1_Ein = m*c*T2 "Using T2 only" W2_Ein=m*(ENTHALPY(Steam_IAPWS,T=T2,x=1)-ENTHALPY(Steam_IAPWS,T=T2,x=0)) "Using h_fg
@NikolaiGermatsky
@NikolaiGermatsky 17 күн бұрын
there are 15* people total. two are waiting besides the 13 machines being used.
@SuemonKwok
@SuemonKwok 17 күн бұрын
Disclaimer the code is has been uploaded to anti cheat software such as Turnitin. Use it to check your answer. m=3.6 [kg] T1=120 [C] x1=1 P2=500 [kPa] T2=300 [C] u1=INTENERGY(Steam_IAPWS,T=T1,x=x1) u2=INTENERGY(Steam_IAPWS,T=T2,P=P2) "Noting that Eout=0 and dU_system=m*(u2-u1), applying energy balance E_in-E_out=dE_system gives" E_out=0 E_in=m*(u2-u1) "Some Wrong Solutions with Common Mistakes:" cp_steam=1.8723 [kJ/kg-K] cv_steam=1.4108 [kJ/kg-K] W1_Ein=m*cp_Steam*(T2-T1) "Assuming ideal gas and using cp" W2_Ein=m*cv_steam*(T2-T1) "Assuming ideal gas and using cv" W3_Ein=u2-u1 "Not using mass" h1=ENTHALPY(Steam_IAPWS,T=T1,x=x1) h2=ENTHALPY(Steam_IAPWS,T=T2,P=P2) W4_Ein=m*(h2-h1) "Using enthalpy"
@SuemonKwok
@SuemonKwok 17 күн бұрын
Disclaimer the code is has been uploaded to anti cheat software such as Turnitin. Use it to check your answer. m=1.5 [kg] T1=12 [C] T2=95 [C] Q_loss=0 [kJ] W_e=0.8 [kJ/s] c=4.18 [kJ/kg-K] time*W_e-Q_loss = dU_system "time in minutes" "from energy balance E_in-E_out=dE_system" dU_system=m*c*(T2-T1) time_min=time/60 "Some Wrong Solutions with Common Mistakes:" W1_time*60*W_e-Q_loss = m*c*(T2+T1) "Adding temperatures instead of subtracting" W2_time*60*W_e-Q_loss = c*(T2-T1) "Not using mass"
@SuemonKwok
@SuemonKwok 17 күн бұрын
Disclaimer the code is has been uploaded to anti cheat software such as Turnitin. Use it to check your answer. m=75 [kg] time=15*60 [s] W_e=2 [kJ/s] R=0.287 [kJ/kg-K] cv=0.718 [kJ/kg-K] time*W_e=m*cv*DELTAT "from energy balance E_in-E_out=dE_system" "Some Wrong Solutions with Common Mistakes:" cp=1.005 [kJ/kg-K] time*W_e=m*cp*W1_DELTAT "Using cp instead of cv" time*W_e/60=m*cv*W2_DELTAT "Using min for time instead of s"
@SuemonKwok
@SuemonKwok 17 күн бұрын
Disclaimer the code is has been uploaded to anti cheat software such as Turnitin. Use it to check your answer. m=5 [kg] Q_loss=300 [kJ] time=10*60 [s] W_e=2 [kJ/s] c=4.18 [kJ/kg-K] time*W_e-Q_loss = dU_system "from energy balance E_in-E_out=dE_system" dU_system=m*c*DELTAT "Some Wrong Solutions with Common Mistakes:" time*W_e = m*c*W1_T "Ignoring heat loss" time*W_e+Q_loss = m*c*W2_T "Adding heat loss instead of subtracting" time*W_e-Q_loss = m*1.0*W3_T "Using specific heat of air or not using specific heat"
@SuemonKwok
@SuemonKwok 18 күн бұрын
Disclaimer the code is has been uploaded to anti cheat software such as Turnitin. Use it to check your answer. m_w=0.32 [kg] T1=20 [C] T2=0 [C] c=4.18 [kJ/kg-K] h_melting=334 [kJ/kg-K] DELTAT=T2-T1 "Noting that there is no energy transfer with the surroundings and the latent heat of melting of ice is transferred form the water, and applying energy balance E_in-E_out=dE_system to ice+water gives" dE_ice+dE_w=0 dE_ice=m_ice*h_melting dE_w=m_w*c*DELTAT "Some Wrong Solutions with Common Mistakes:" W1_mice*h_melting*(T1-T2)+m_w*c*DELTAT=0 "Multiplying h_latent by temperature difference" W2_mice=m_w "taking mass of water to be equal to the mass of ice
@SuemonKwok
@SuemonKwok 18 күн бұрын
Disclaimer the code is has been uploaded to anti cheat software such as Turnitin. Use it to check your answer. m=5 [kg] P_1=400 [kPa] T=30 [C] Wout_b=15 [kJ] Win_pw=3 [kJ] R=0.287 [kJ/kg-K] cv=0.718 [kJ/kg-K] Q_in+Win_pw-Wout_b=0 "From energy balance E_in-E_out=dE_system, T=constant and thus dE_system=0" "Some Wrong Solutions with Common Mistakes:" W1_Qin=Q_in/cv "Dividing by cv" W2_Qin=Win_pw+Wout_b "Adding both quantities" W3_Qin=Win_pw "Setting it equal to paddle-wheel work" W4_Qin=Wout_b "Setting it equal to boundaru work"
@SuemonKwok
@SuemonKwok 18 күн бұрын
Disclaimer the code is has been uploaded to anti cheat software such as Turnitin. Use it to check your answer. N=3 [kmol] T_change=10 [C] Ru=8.314 [kJ/kmol-K] Q_diff=N*Ru*T_change "cp-cv=R, and thus Q_diff=m*R*dT=N*Ru*dT" "Some Wrong Solutions with Common Mistakes:" W1_Qdiff=0 "Assuming they are the same" W2_Qdiff=Ru*T_change "Not using mole numbers" W3_Qdiff=Ru*T_change/N "Dividing by N instead of multiplying" W4_Qdiff=N*Rair*T_change; Rair=0.287 "using Ru instead of R"
@SuemonKwok
@SuemonKwok 18 күн бұрын
Disclaimer the code is has been uploaded to anti cheat software such as Turnitin. Use it to check your answer. m=75 [kg] P_1=100 [kPa] T_1=15 [C] time=30*60 [s] W_ref=0.250 [kJ/s] W_TV=0.120 [kJ/s] W_heater=1.8 [kJ/s] W_fan=0.05 [kJ/s] R=0.287 [kJ/kg-K] "Applying energy balance E_in-E_out=dE_system gives E_out=E_in since T=constant and dE=0" E_gain=W_ref+W_TV+W_heater+W_fan Q_loss=E_gain*Convert(kJ/s, kJ/h) "Some Wrong Solutions with Common Mistakes:" E_gain1=-W_ref+W_TV+W_heater+W_fan "Subtracting Wrefrig instead of adding" W1_Qloss=E_gain1*3600 "kJ/h" E_gain2=W_ref+W_TV+W_heater-W_fan "Subtracting Wfan instead of adding" W2_Qloss=E_gain2*3600 "kJ/h" E_gain3=-W_ref+W_TV+W_heater-W_fan "Subtracting Wrefrig and Wfan instead of adding" W3_Qloss=E_gain3*3600 "kJ/h" E_gain4=W_ref+W_heater+W_fan "Ignoring the TV" W4_Qloss=E_gain4*3600 "kJ/h"
@SuemonKwok
@SuemonKwok 18 күн бұрын
Disclaimer the code is has been uploaded to anti cheat software such as Turnitin. Use it to check your answer. m=60 [kg] P1=200 [kPa] T1=25 [C] Qsol=0.8 [kJ/s] time=30*60 [s] Wfan=0.12 [kJ/s] R=0.287 [kJ/kg-K] cv=0.718 [kJ/kg-K] time*(Wfan+Qsol)=m*cv*(T2-T1) "from energy balance E_in-E_out=dE_system" "Some Wrong Solutions with Common Mistakes:" cp=1.005 [kJ/kg-K] time*(Wfan+Qsol)=m*cp*(W1_T2-T1) "Using cp instead of cv " time*(-Wfan+Qsol)=m*cv*(W2_T2-T1) "Subtracting Wfan instead of adding" time*Qsol=m*cv*(W3_T2-T1) "Ignoring Wfan" time*(Wfan+Qsol)/60=m*cv*(W4_T2-T1) "Using min for time instead of s"
@SuemonKwok
@SuemonKwok 19 күн бұрын
Disclaimer the code is has been uploaded to anti cheat software such as Turnitin. Use it to check your answer. V1=0.5 [m^3] V2=0.2 [m^3] P1=600 [kPa] T1=300 [K] R=8.314/28 P1*V1=m*R*T1 W=m*R*T1* ln(V1/V2) "constant temperature process" "Some Wrong Solutions with Common Mistakes:" W1_W=R*T1* ln(V2/V1) "Forgetting m" W2_W=P1*(V1-V2) "Using V*DeltaP" P1*V1/T1=P2*V2/T1 W3_W=(V1-V2)*(P1+P2)/2 "Using P_ave*Delta V" W4_W=P1*V1-P2*V2 "Using W=P1V1-P2V2"
@SuemonKwok
@SuemonKwok 19 күн бұрын
Disclaimer the code is has been uploaded to anti cheat software such as Turnitin. Use it to check your answer. V=3 [m^3] P1=500 [kPa] T1=300 [K] P2=800 [kPa] W=0 "since constant volume" "Some Wrong Solutions with Common Mistakes:" R=0.297 W1_W=V*(P2-P1) "Using W=V*DELTAP" W2_W=V*P1 W3_W=V*P2 W4_W=R*T1*ln(P1/P2)
@pauljojo831
@pauljojo831 21 күн бұрын
Thanks
@SuemonKwok
@SuemonKwok 21 күн бұрын
Thanks for watching
@SuemonKwok
@SuemonKwok 24 күн бұрын
Disclaimers code has been uploaded to anti cheat software such as Turnitin. If you plan on using it change it up. Vol_A=0.2 [m^3] P_A[1]=400 [kPa] x_A[1]=0.8 T_B[1]=250 [C] P_B[1]=200 [kPa] Vol_B=0.5 [m^3] T_final=25 [C] E_in-E_out=DELTAE E_in=0 E_out=Q_out DELTAE=m_A*(u_A[2]-u_A[1])+m_B*(u_B[2]-u_B[1]) m_A=Vol_A/v_A[1] m_B=Vol_B/v_B[1] Fluid$='Steam_IAPWS' u_A[1]=INTENERGY(Fluid$,P=P_A[1], x=x_A[1]) v_A[1]=volume(Fluid$,P=P_A[1], x=x_A[1]) T_A[1]=temperature(Fluid$,P=P_A[1], x=x_A[1]) u_B[1]=INTENERGY(Fluid$,P=P_B[1],T=T_B[1]) v_B[1]=volume(Fluid$,P=P_B[1],T=T_B[1]) u_B[2]=u_final u_A[2]=u_final m_final=m_A+m_B Vol_final=Vol_A+Vol_B v_final=Vol_final/m_final u_final=INTENERGY(Fluid$,T=T_final, v=v_final) P_final=pressure(Fluid$,T=T_final, v=v_final)
@zakariaibrahim6781
@zakariaibrahim6781 24 күн бұрын
which edition of the book are you using ? thanks for sharing ❤
@SuemonKwok
@SuemonKwok 24 күн бұрын
9
@SuemonKwok
@SuemonKwok 28 күн бұрын
Disclaimer the code has been uploaded to anti cheat software such as Turnitin. Change it up if you plan on using it. V = 0.3 [L] T_1_ice = 0 [C] T_1 = 20 [C] T_2 = 5 [C] c_ice = 2.11 [kJ/kg-C] c_water = 4.18 [kJ/kg-C] h_if = 333.7 [kJ/kg] T_1_ColdWater = 0 [C] rho_water = 1 [kg/L] m_water = rho_water*V E_in - E_out = DELTAE_sys E_in = 0 E_out = 0 DELTAE_sys = DELTAU_water+DELTAU_ice "The system is water+ice" DELTAU_water = m_water*C_water*(T_2 - T_1) T_melting = 0 [C] DELTAU_ice = DELTAU_solid_ice+DELTAU_melted_ice DELTAU_solid_ice =m_ice*c_ice*(T_melting-T_1_ice) + m_ice*h_if DELTAU_melted_ice=m_ice*c_water*(T_2 - T_melting) m_ice_grams=m_ice*convert(kg,g) DELTAE_sys = DELTAU_water+DELTAU_ColdWater "The system is water+cold water" DELTAU_water = m_water*c_water*(T_2_ColdWater - T_1) DELTAU_ColdWater = m_ColdWater*c_water*(T_2_ColdWater - T_1_ColdWater) m_ColdWater_grams=m_ColdWater*convert(kg,g)
@danielmccrobie9241
@danielmccrobie9241 Ай бұрын
how can you just assume the boundary work is 0? that was the only part that didn't make sense to me.
@SuemonKwok
@SuemonKwok Ай бұрын
The assumption that the boundary work is zero in this problem is due to the fact that the process is carried out at a constant pressure. In a piston-cylinder device, the boundary work is done when the volume of the system changes. However, in this case, the volume change is due to the evaporation of the liquid, not due to the movement of the piston. Therefore, the work associated with the volume change is considered as part of the internal energy change of the system, not as boundary work.
@no_one_special7011
@no_one_special7011 Ай бұрын
I hope you much successful as an educator your videos and explanations are amazing I use them to studying for thermodynamics exams and have gotten good grades thank you
@SuemonKwok
@SuemonKwok Ай бұрын
Thanks for watching, congratulations on your results. Learning is a journey. My earlier videos were a stepping stone on improving how to get the message across in thermodynamics. I try to improve with each video. I do put disclaimers in every video where I might make calculation mistakes and encourage students to try the tutorial themselves.
@arinkeskin2543
@arinkeskin2543 Ай бұрын
But the plate is turning??
@SuemonKwok
@SuemonKwok Ай бұрын
For foods that cover the entire plate won't matter too much but for smaller items placing it offset, it will cover the dead zones when the microwaves bounces and miss the center
@muhammadhaziq2456
@muhammadhaziq2456 Ай бұрын
the equation is change in internal energy but why you use change in enthalpy???can you explain
@SuemonKwok
@SuemonKwok Ай бұрын
VI∆t+W_(pw,in) = ∆U Remember we are trying to find voltage. For a conceptual point of view see reasoning below The reason we use change in enthalpy (ΔH) instead of change in internal energy (ΔU) in this problem is due to the nature of the process. In thermodynamics, the change in internal energy (ΔU) is used when we are dealing with a closed system where no matter is exchanged with the surroundings, and the only work done is boundary work (expansion or compression of the system). However, in this problem, we have a constant-pressure process in an open system (since mass is leaving the system due to evaporation).
@crstnmts_uitm
@crstnmts_uitm Ай бұрын
Thank you very much!
@SuemonKwok
@SuemonKwok Ай бұрын
Thanks for watching
@busrabs75
@busrabs75 Ай бұрын
what is the name of this book ? ?
@SuemonKwok
@SuemonKwok Ай бұрын
Most of it is from Yunus and Cengal Introduction to thermodynamics years 1 and 2 Some questions were thrown in the tutorial by the lecturer
@abenezerembet7999
@abenezerembet7999 Ай бұрын
Where is the file pls attach it
@mad_.spider
@mad_.spider Ай бұрын
Sir is it good moving to newzealand for chemical engineers . Will they have good job opportunities or any good destination
@SuemonKwok
@SuemonKwok Ай бұрын
Australia is better in terms of true chemical engineers. In New Zealand chemical engineers are mainly farming related such as pestides, water plant treatments, some pharmaceuticals, manufacturing for coating. It's a mixture of process and chemical combined Far fewer only handful options on seek.co.nz compare to Australia
@mad_.spider
@mad_.spider Ай бұрын
@@SuemonKwok I'm thinking to go to a country where we can get a PR easily after getting job . So please suggest me some rare countries.
@SuemonKwok
@SuemonKwok Ай бұрын
@@mad_.spider I wouldn't know. Never left NZ. It takes 2 years of living in NZ to get PR however the cost of living in NZ is pretty high. Wages are low compared to Austrailia which is 2 hours flight across the ocean. A quick search for lowest living time within the countries to get PR is Aus, NZ at 2 years Canada at 730 days (also 2 years) EU at 3 years
@mad_.spider
@mad_.spider Ай бұрын
@@SuemonKwok will we get jobs right after completion of masters in newzealand i mean for freshers who just completed their studies
@SuemonKwok
@SuemonKwok Ай бұрын
@@mad_.spider No guarantees, it depends on the job market at that time. It comes down to luck when applying for jobs and what each company needs.
@greatorial1672
@greatorial1672 Ай бұрын
Be blessed. YOU ARE HELPING SOMEONE, TRULYY!!
@SuemonKwok
@SuemonKwok Ай бұрын
Thanks for watching
@emmanuelrambaran3017
@emmanuelrambaran3017 Ай бұрын
Im thinking about migratung go newzealand to live and work from Trinidad
@HomelyRollout
@HomelyRollout Ай бұрын
At 6:15 how did you know to use the internal energy values in the middle column? Aren't the left and right columns also encompassing the the range of 3040?
@HomelyRollout
@HomelyRollout Ай бұрын
Also, likewise, at 3:13 why couldn't you have used the pressure to find the internal energy?
@SuemonKwok
@SuemonKwok Ай бұрын
@@HomelyRollout Yes you are correct on both fronts. It appears I've used the wrong slides. It has been added pinned comment and added to community notes. I apologize for these mistakes.
@SuemonKwok
@SuemonKwok Ай бұрын
Frequently Asked Questions. Why is it V_1 - V_2 not V_2 - V_1 ( V_2 < V_1 ), then ( V_1 - V_2 ) will be a positive number. However, in thermodynamics, the sign convention for work is such that work done by the system on the surroundings is considered positive, and work done on the system by the surroundings is considered negative. So, when a gas is compressed (like in your piston-cylinder device), the volume decreases (( V_2 < V_1 )), and the surroundings do work on the system. According to the convention, this work is negative, which is why we use ( P(V_1 - V_2) ) and not ( P(V_2 - V_1) ). The formula ( W = P(V_1 - V_2) ) inherently accounts for this sign convention by giving a negative result for compression work. To put it simply, the formula ( W = P(V_1 - V_2) ) ensures that the work is negative for compression because ( V_1 ) is greater than ( V_2 ), and the work is positive for expansion because ( V_1 ) would be less than ( V_2 ). This sign convention is consistent with the first law of thermodynamics, which in one form can be written as: ΔU=Q-W If work is done on the system (compression), ( W ) is negative, and the internal energy ( U ) increases. Conversely, if the system does work on the surroundings (expansion), ( W ) is positive, and the internal energy decreases. Part B Why do we use 1000 kPa not 500 kPa The reason we use 1000 kPa in the work calculation for part (b) is because the work done is calculated up to the point where the piston hits the stops, not the final state of the system. In this problem, the stops are set at 40% of the initial volume. This means that the piston can only compress the steam up to this volume before it hits the stops and can no longer do work on the system. At this point, the pressure inside the cylinder is still 1000 kPa, which is the initial pressure. After the piston hits the stops, the system continues to cool down until it reaches the final pressure of 500 kPa. However, during this cooling process, the volume of the system remains constant because the piston is not moving. Therefore, no work is done on the system during this stage. So, the work calculated is the work done during the compression process up to the point where the piston hits the stops, which is why we use the initial pressure of 1000 kPa in the calculation. The final pressure of 500 kPa is not used in the work calculation because no work is done on the system after the piston hits the stops.
@MxOGN
@MxOGN Ай бұрын
sry but really bad explaining, no stetps
@SuemonKwok
@SuemonKwok Ай бұрын
kzbin.info/www/bejne/jnWnm6p4ps1sh7c try this video instead
@carlosmolina8805
@carlosmolina8805 Ай бұрын
Why we use mP(v1-v2) instead of mP(v2-v1)
@SuemonKwok
@SuemonKwok Ай бұрын
The reason we use ( V_1 - V_2 ) instead of ( V_2 - V_1 ) is because work is considered positive when done by the system and negative when done on the system. Since compression means work is done on the gas, reducing its volume, the work is negative, and thus we have ( V_1 - V_2 ).
@carlosmolina8805
@carlosmolina8805 Ай бұрын
@@SuemonKwok But to be negative, v2 < v1, so if we use (v1-v2), the work always going to be positive
@SuemonKwok
@SuemonKwok Ай бұрын
( V_2 < V_1 ), then ( V_1 - V_2 ) will be a positive number. However, in thermodynamics, the sign convention for work is such that work done by the system on the surroundings is considered positive, and work done on the system by the surroundings is considered negative. So, when a gas is compressed (like in your piston-cylinder device), the volume decreases (( V_2 < V_1 )), and the surroundings do work on the system. According to the convention, this work is negative, which is why we use ( P(V_1 - V_2) ) and not ( P(V_2 - V_1) ). The formula ( W = P(V_1 - V_2) ) inherently accounts for this sign convention by giving a negative result for compression work. To put it simply, the formula ( W = P(V_1 - V_2) ) ensures that the work is negative for compression because ( V_1 ) is greater than ( V_2 ), and the work is positive for expansion because ( V_1 ) would be less than ( V_2 ). This sign convention is consistent with the first law of thermodynamics, which in one form can be written as: ΔU=Q-W If work is done on the system (compression), ( W ) is negative, and the internal energy ( U ) increases. Conversely, if the system does work on the surroundings (expansion), ( W ) is positive, and the internal energy decreases.
@carlosmolina8805
@carlosmolina8805 Ай бұрын
@@SuemonKwok So, for "logic" we already know that work is going to be negative because v1>v2, so that is ok. The only thing that I do not understand is why we use P=1000 kPa, I do not have any information to use that formula, formula for constants pressions...
@SuemonKwok
@SuemonKwok Ай бұрын
​@@carlosmolina8805 The reason we use 1000 kPa in the work calculation for part (b) is because the work done is calculated up to the point where the piston hits the stops, not the final state of the system. In this problem, the stops are set at 40% of the initial volume. This means that the piston can only compress the steam up to this volume before it hits the stops and can no longer do work on the system. At this point, the pressure inside the cylinder is still 1000 kPa, which is the initial pressure. After the piston hits the stops, the system continues to cool down until it reaches the final pressure of 500 kPa. However, during this cooling process, the volume of the system remains constant because the piston is not moving. Therefore, no work is done on the system during this stage. So, the work calculated is the work done during the compression process up to the point where the piston hits the stops, which is why we use the initial pressure of 1000 kPa in the calculation. The final pressure of 500 kPa is not used in the work calculation because no work is done on the system after the piston hits the stops. Hope this helps
@carlosmolina8805
@carlosmolina8805 Ай бұрын
Why we use mP(v1-v2) instead of mP(v2-v1)
@dilloncarver3636
@dilloncarver3636 Ай бұрын
Where are you getting the heights for h in the Ptop and Pbot equations?
@SuemonKwok
@SuemonKwok Ай бұрын
You convert the mmhg ( millimeters of mercury) to mhg (meters of mercury) which roughly the same meters 675 mmhg /1000 = 0.675 mhg 695 mmhg/1000 =0.695 mhg
@bavaniraokalisetti9194
@bavaniraokalisetti9194 Ай бұрын
Plz sir i want to join the Newzland
@shadestockton6225
@shadestockton6225 Ай бұрын
what text book is this from
@SuemonKwok
@SuemonKwok Ай бұрын
A combination of different ones Introduction to thermodynamics years 1 and 2 Also Yunus and Cegal Also lecturer notes/problems
@shadestockton6225
@shadestockton6225 Ай бұрын
@@SuemonKwok what is the name of the person who wrote the book
@SuemonKwok
@SuemonKwok Ай бұрын
@@shadestockton6225 Most of it is written by Yunus and Cegal. Not sure who wrote introduction to thermodynamics year 1 and 2. It's 1995 photocopy
@matthewsuh8787
@matthewsuh8787 2 ай бұрын
Hi, I think I found out what you did wrong on row 2 of the table. The formula for finding the quality of a liquid-vapor region is actually x= (h-h_f)/(h_fg). When using the given value h=1800, you'll get x = (1800 - 589.16)/2144.3 This will get you x ~ 0.565
@SuemonKwok
@SuemonKwok 2 ай бұрын
Yes, you are correct. Those earlier videos I was rusty haven't used thermo in years.
@engkanti324
@engkanti324 2 ай бұрын
How can i get a QS job in NZ from India, please suggest.
@SuemonKwok
@SuemonKwok 2 ай бұрын
See NZiQS website for details. QS is in demand and on the green list for immigration according to the website www.nziqs.co.nz/Membership/International-Membership#2415102-immigrating-to-new-zealand
@tumisangphiri648
@tumisangphiri648 2 ай бұрын
When calculating the pressure difference, why was 10.3 used and not 15.4
@SuemonKwok
@SuemonKwok 2 ай бұрын
The value of 10.3 kW is the mechanical power output of the pump, which is the useful power output doing work on the fluid. The 15.4 kW is the electrical power input to the pump-motor unit. The overall efficiency of the pump-motor unit is defined as the ratio of the mechanical power output (the useful power output) to the electrical power input. In this case, the mechanical power output is 10.3 kW (which is used to pump the water), and the electrical power input is 15.4 kW (which is the total power consumed by the pump). So, when calculating the pressure difference, we use the mechanical power output (10.3 kW), not the electrical power input (15.4 kW), because the pressure difference is related to the work done on the fluid, which is represented by the mechanical power output. The rest of the power input (15.4 kW - 10.3 kW = 5.1 kW) is lost as waste heat due to inefficiencies in the pump-motor unit.
@tumisangphiri648
@tumisangphiri648 2 ай бұрын
@@SuemonKwok alright Sir,thank you