HW1-ARE 346N-BES-F20-Solutions-PDF (2).pdf

10/20/2020 HW2-ARE 346N-BES-F20-Solutions - Colaboratory https://colab.research.google.com/drive/1ggGirkwmJoZ-jcb8BemptYpUNLPLhgES#scrollTo=-pBSsﬂz_JyZ&printMode=true 1/12 Homewo rk 1 ARE 346N Building Environmental Systems Professor Dr. Zoltan Nagy Due: September 29th, 2020 Solve each of the following problems and show your work. Make sure to label each answer with the same label as the problem. You will be graded on both the correct method and solution. Partial credit is awarded for use of the correct equation or method, correct values chosen from tables and charts when required, and the correct answer with appropriate units. This assignment includes TWO problems. PROBLEM POINTS 1.a 3 pts 1.b 2 pts 1.c 3 pts 1.d 3 pts 1.e 3 pts 1.f 3 pts 2.a 18 pts TOTAL 35 pts Instructions For this Homework, the following resources might be useful for you: 1. Psychrometric Chart 1. Online Interactive Chart 2. Downloadable Charts 2. Table 3.6 from your textbook- Chapter 3 3. Table 3.7 from your textbook- Chapter 3 Resources

10/20/2020 HW2-ARE 346N-BES-F20-Solutions - Colaboratory https://colab.research.google.com/drive/1ggGirkwmJoZ-jcb8BemptYpUNLPLhgES#scrollTo=-pBSsﬂz_JyZ&printMode=true 2/12 Problems Outdoor air with dry bulb temperature of 40 o F and relative humidity of 60% is heated using an electric heater to DBT= 95 o F, and after that humidi±ed to relative humidity of 35% by injection of dry steam. Problem 1 - Psychrometrics Draw the heating and humidifying process in psychrometric chart. Show all points. Problem-1(a) # YOUR CODE HERE #

10/20/2020 HW2-ARE 346N-BES-F20-Solutions - Colaboratory https://colab.research.google.com/drive/1ggGirkwmJoZ-jcb8BemptYpUNLPLhgES#scrollTo=-pBSsﬂz_JyZ&printMode=true 3/12 Using the psychrometric chart, determine the amount of energy supplied to 1 lb of dry air in this heating and humidifying processes Problem-1(b) # YOUR CODE HERE # 23.5 #enthalpy of external air h1=13.1 # Btu/lbda #enthalpy of air after humidifier h3=36.6 #Btu/lbda #Energy per unit of mass: q13=h3-h1 print(q13) Problem-1(c)

10/20/2020 HW2-ARE 346N-BES-F20-Solutions - Colaboratory https://colab.research.google.com/drive/1ggGirkwmJoZ-jcb8BemptYpUNLPLhgES#scrollTo=-pBSsﬂz_JyZ&printMode=true 4/12 Find the amount of water while steam humidi±er is using for humidi±cation of 1 lb dry air. Assume that all water is converted into steam. # YOUR CODE HERE E 0.0092 w3= 0.0124 #lbw/lbda w2=0.0032 #lbw/lbda Delta_w23= w3-w2 print(Delta_w23) w If the volume ²ow rate of air is 30 ft3/min (CFM), what is the amount of energy per hour (energy rate) [Btu/h] needed for heating and humidi±cation? What is the ²ow rate of water (lbw/hour) needed for humidi±cation? Problem-1(d) 1815.0 1335.84 3172.5 3150.84 0.11536363636363636 # YOUR CODE HERE #Volume flow rate V=30 #ft3/min Qsensible = 1.1 * V * (95-40) Q_latent = 4840*V*(Delta_w23) Q_total= 4.5*V*q13 print(Qsensible) print(Q_latent) print(Q_total) print(Qsensible+Q_latent) GPM = Q_total / (500 * (95-40)) print(GPM) #

10/20/2020 HW2-ARE 346N-BES-F20-Solutions - Colaboratory https://colab.research.google.com/drive/1ggGirkwmJoZ-jcb8BemptYpUNLPLhgES#scrollTo=-pBSsﬂz_JyZ&printMode=true 5/12 3214.7999999999997 1.25856 #ALternative Solution : I accepted the solutions above because of the book's reference #Volume flow rate V=30 #ft3/min Air_density=0.076 #lb/ft3 m = V*Air_density * 60 #Air mass flow rate lb/hr #Total heat rate: Qtotal = m*q13 #[Btu/h] #Water flow rate: G= m*Delta_w23 print(Qtotal) print(G) # What is the sensible energy that electric heater provides per unit of air? What should be the power of electric heater for heating of 30 ft3/min of air ±ow? Assume that there is no heat loss in electric heater. Problem-1(e) # YOUR CODE HERE E 545.25273408 1860.4799999999998 h2=26.7 #Btu/lbda qsensible= h2 - h1 #Btu/lb Qsensible= m*qsensible #Power of electric heater is equal of sensible heat rate: P= Qsensible # [Btu/h] #Wattconversion Power_Watt_electricHeater= P*0.293071 print(Power_Watt_electricHeater) print(Qsensible) h

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