EME 811
Solar Thermal Energy for Utilities and Industry

5.4. Assignment


Thermal fluids have several key properties that need to be carefully considered when selecting a fluid for a specific application. These properties include maximum temperature, freezing temperature, density, vapor pressure, specific heat, enthalpy, and viscosity. By performing calculations, one can save a significant amount of money that would otherwise be spent on trial and error experiments and extra equipment, which potentially can be avoided.

This assignment is a series of short analytical problems dealing with thermal fluid assessment. Some problems will require conceptual explanation and some will involved quantitative calculations.


There are two heat transfer fluids - oils that are similar in cost, quality, and expected lifetime. Here are their technical characteristics:

Oil A:

Tmax = 300°C
Tfreeze = -10°C
Cp = 1.7 kJ/kgK (specific heat)
ρ = 800 kg/m3 (density)

Oil B:

Tmax = 395°C
Tfreeze = 13°C
Cp = 2.3 kJ/kgK (specific heat)
ρ = 700 kg/m3 (density)

Range of reasonable Darcy Friction Factors:

0.01 > fd > 0.09 (for problem 3, use fd = 0.04)

Tin = 150°C

Tout = 280 oC

Answer the following questions:

  1. Which of the two fluids above should be used, and why, if the process requires a temperature of (a) 380°C, (b) 300 oC?
  2. If the system is required to output 2 MW of thermal energy, what should the mass flow rate (kg/hr) be with Oil A? What about with Oil B? (Hint: you can use equation 10.1.2 from the D&B book to develop this problem), 
  3. Based on results from Question 2, for each of the two oils, calculate the flow speed (m/s) in a pipe with an inner diameter of 3 cm?
  4. What is the resulting pumping head loss for each fluid in a 200 m long collector pipe with Darcy Friction Factor of fd = 0.04?
  5. Based on results from Questions 3 and 4, calculate the pumping power required for each fluid’s head loss and associated annual costs of energy, considering rate $0.10/kWh and system's capacity factor of 20% over the year (i.e., it is pumping 20% of the time). Discuss the difference in pumping power (or cost) between the fluids. 

List all your answers in the comparative table Oil A vs Oil B and include it in the end of your report.

Deliverable - Lesson 5 Assignment

The problems can be either typed (size 12 Times New Roman or equivalent font) or hand-written as scanned (like in previous lessons). Please submit your solutions in a single PDF file to Lesson 5 assignment dropbox in Canvas. Remember to show all key equations and analytical steps you take in your solution.