EME 811
Solar Thermal Energy for Utilities and Industry

5.0 Introduction

Imagine that thermal fluid plays the same role in plant processes as blood in the human body. It is thus inextricably linked to the optimum functioning of the entire system; if cholesterol deposits congest arteries, then that directly affects the heart, which unfortunately leads to the organism shutting down.


— globalheattransfer.co.uk

Thermal fluids are used to move heat through a system. A system could be composed of solar collectors, storage tanks, heat exchangers, valves, pipes, and more. Through all of these components flow a fluid that carries the heat from one point to another within the system. In a heat exchanger, one fluid flows next to another fluid (e.g., air and water) and heat flows from the hotter fluid to the colder fluid (e.g., from a hot air stream to cold water, effectively cooling the air). In a storage tank, the fluid holds the heat and waits to be pumped to where the heat can be used. In a solar collector, the fluid passes through a tube (or pipe) that is either joined to black, radiation absorbing fins (flat plate collector) or contained within a vacuum glass tube (parabolic troughs) or a combination of both (evacuated tube collector). Selecting a thermal fluid requires knowledge of the physical properties of each fluid under different thermal conditions.

Learning Objectives

  • Describe the available and developing thermal fluids used in solar thermal energy systems.
  • Discuss relevant issues (i.e. cost, corrosivity, etc.) associated with available and developing thermal fluids.
  • Apply thermal conductivity calculations.
  • Apply heat capacity calculations.
  • Select the proper working fluids for various applications.

What is due for Lesson 5?

This lesson will take us one week to complete. The list of assignments for this lesson is provided in the table below. More detailed instructions are given on respective pages of this lesson and in Canvas modules.

Tasks Assignment Details Access/Directions



This report presents a detailed heat transfer model for tubular absorber system and also includes equations and calculations for heat transfer to heat trasnfer fluids. It is a nice resource to supplement the theory from the D&B book.

All reading materials for this lesson can be accessed online via links provided.
Assignment Comparative assessment of heat transfer fluids Specific directions are provided on the respective page of this lesson.
Quiz Take the Lesson 5 Reading Quiz. Registered students can access the quiz in the Lesson 5 Module in Canvas.
Discussion  What makes a thermal fluid the top choice for solar project managers? Please read directions and post your reflection in Lesson 5 Discussion in Canvas.


If you have any questions, please post them to our Questions and Answers discussion forum in Canvas. I will check that discussion forum daily to respond. While you are there, feel free to post your own responses if you, too, are able to help out a classmate.