# Homework, Quizzes, Simulation Examples - Intro to Heat Transfer

## Simulation Examples

Several simulation examples are provided here. Each of them comes with a description file, video instructions, and an Ansys simulation file. All the simulations are conducted using Ansys software. Download the student version of Ansys simulation software here.

### (1) Heat transfer of a teapot

Metal and porcelain are two common materials for teapots. Assume a teapot is filled with a certain amount of boiling water. How do the temperature distributions of the metal teapot and the porcelain one differ?

In this example, we will perform thermal analysis to find out the temperature distribution of the two types of teapot using both steady-state thermal and transient thermal analysis. Check and compare the results between the two teapot types and also between steady-state analysis and transient analysis. Are the results expected and reasonable? Download the zip file and extract the contents. Go through the Readme file. Follow along with the provided How To Video file.

### (2) Steel pot on a stove

The three modes of heat transfer are conduction, convection and radiation.  Here, we provide a simulation example to demonstrate the different modes. A steady-state thermal analysis is performed for the steel pot with hot liquid in it. Follow the steps to learn how the three heat transfer modes are defined in the simulation. Download the zip file and extract the contents. Go through the Readme file. Follow along with the provided How To Video file.

## Homework

### (1) Solar panel

Solar panels convert solar energy to electric energy, which can be stored. The changing orientation of the sun's rays during  the day will affect the amount of solar energy absorbed by the panel. At the same time, pointing the panel in the optimal direction for different geographic locations also influences the efficiency of converting solar energy.

Here, we represent the sun/solar panel system as a solid ball generating heat and a panel receiving the heat. The dimensions of the components and the distance between them are not designed to be realistic in this case. We intend to use this simple model to learn about temperature and heat flux distribution caused by radiation. Free convection on the surface of panel is not considered here.

Follow the instructions to set up the model and evaluate the results using your knowledge of heat transfer:

(1) Check out the temperature distribution and heat flux distribution. Heat flux hasn't been introduced in detail yet. Here, based on the results plotted on the panel, try to think about what kind of quantity heat flux is.

(2) Move the panel or the solid ball toward or away from each other. The distance and the angle between the two components will change. Check out the results and consider if they are reasonable.

Radiation and convection are the primary modes of heat transfer in an oven for baking food. In addition, a small layer of food that is directly in contact with the baking tray, heats up due to conduction. There are two types of ovens on the market: conventional and convection. A conventional oven does not have fans and primarily uses radiation from the heating elements inside the oven to cook food. To a smaller extent, food also heats up due to natural convection (caused by a difference in temperatures in different portions of the oven). A convection oven has fans inside and forced convection (caused by the fans) is an important source of heat transfer. Since the radiation is constant in both the ovens, in this problem we will disregard the radiation and focus on the difference between natural and forced convection.

Follow the instructions to simulate the heating up of a gingerbread cookie inside (a) a conventional oven and (b) convection oven, and answer the following questions:

(a) If the gingerbread cookie needs to reach a temperature of at least 200oC to be completely baked, how much time will it take to finish baking the cookie in the two types of ovens?

(b) For better flavor and texture, the temperature distribution throughout the cookie needs to be uniform. While you never have a completely uniform distribution of temperature over the entire cookie, which of these two ovens does a better job? Why do you think that is? (Hint: Think about how the rate of convection on the top surface compares with conduction on the bottom surface).

Material properties for the cookie: density = 50 kg m-3; thermal conductivity = 0.3 W m-1 0C-1 (assume this is isotropic); specific heat capacity = 2000 J kg-1 0C-1. Assume that room temperature is 22 0C and the ovens are heated to 250 0C in 200 seconds. The convection coefficient is  2e-5 W mm-2 for the conventional oven and  2e-3 W mm-2 for the convection oven.

Lesson Content