Investigation of Transient Heating/Cooling of an Everyday Object via Conduction Analysis
MIET1081 Heat Transfer
2.1 Object Selection
In the everyday world, countless objects experience natural heating or cooling due to their interaction with the surrounding environment. The object chosen for this group investigation is a freshly brewed coffee cup which focuses on its cooling process through a conduction analysis.
The coffee cup’s physical geometry is measured using a precise measurement ruler to obtain the dimensions. The coffee cup used in this conduction analysis closely resembles a cylindrical shape where the diameter of the cup is 0.09 meters, and the height of the cup is 0.085 meters. The coffee cup is made of ceramic and has a typical thermal conductivity of approximately 3.8 W/m.K which is low to help slow down the heat transfer. Furthermore, the ceramic material of the cup has a specific heat capacity of approximately 900 J/g.K which helps it store a good amount of heat. The coffee cup will be filled with milk and coffee where the density of the liquid can be approximated to the properties of liquid water with a density of 1000 kg/m3.
The problem for this cooling analysis is how long it will take for the coffee in the cup to cool down from its high temperature to a room temperature, in a room with an ambient temperature of 17.6 degrees Celsius. The natural typical heat transfer coefficient from the natural convection without any forced convection ranges between 5 to 3000 W/m2k.
In this experiment, the shape of the coffee cup is assumed to be perfectly cylindrical in shape, therefore the constant properties of the coffee such as the thermal conductivity, heat capacity and density will be assumed to be constant throughout the cooling process. The radiation in this experiment will be negligible as there is not much of a contribution compared to conduction and convection.
2.2 Observational or Experimental Setup
The following temperature measurements will be measured using the Google Pixel 8 Pro’s temperature sensor, and its thermometer app. The initial temperature of the ceramic coffee cup sitting in the ambient room of 17.6 degrees Celsius without any liquid is measured at 19 degrees. The temperature of the coffee cup with freshly poured hot coffee is then measured at a high temperature of 59.3 degrees Celsius. The initial temperature of the coffee that came out of the coffee pod machine measured at a temperature of 60.2 degrees Celsius. The physical dimensions of the ceramic coffee cup’s diameter are measured to be 0.09 meters, and the height of the cup is 0.085 meters. Lastly the thickness of the cup is approximately 0.003 meters
Initial temperature of cup (Celsius) = 19
Temperature of cup with hot coffee at t=0 (Celsius) = 59.3
Room temperature (Celsius) = 17
Diameter (m) = 0.09
Height (m) = 0.085
Thickness (m) = 0.003
Density of milk = 1000 kg/m^3
Specific heat of milk = 4186 J/Kg
Temperature of Coffee:
References:
https://thermtest.com/keeping-your-warm-drinks-warm-a-thermal-properties-approach#:~:text=The%20thermal%20conductivity%20of%20a,the%20longest%20amount%20of%20time.
https://driftaway.coffee/coffeecup/#:~:text=Ceramic%20has%20a%20higher%20specific,%E2%80%93%20(800%20J/kj.