ENME 471 Linear Conduction

.pdf

School

University of Calgary *

*We aren’t endorsed by this school

Course

471

Subject

Mechanical Engineering

Date

Apr 3, 2024

Type

pdf

Pages

Uploaded by CountFalcon4077

ENME 471 Heat Transfer Laboratory Experiment 1: Linear Heat Conduction Objectives and Purpose: i) To develop an understanding of temperature measurement fundamentals and uncertainty by taking quantitative measurements using thermocouples. ii) To show how heat conducts linearly along a solid bar of uniform dimensions and material. iii) To demonstrate how experimental work can be used to determine the material of a solid by applying the principals of one-dimensional conduction in a solid (Chapter 3 of Incropera and DeWitt). Introduction: One-dimensional heat transfer is used extensively for the analysis of many different types of heat transfer problems. The experiment performed here involves what can be approximated as one- dimensional conduction through a rod of unknown material, with a constant temperature on one side set by water heated by a heater. The heat is conducted through the rod, and seven thermocouples are used to determine the temperature distribution axially along the rod, as seen in Figure 1. The experimentalist must apply the fundamentals of one-dimension conduction in a solid to perform a linear regression of the temperature profile along the solid material. From this, tables of typical thermal conductivities of various solids will be referenced, and the material will be determined. Apparatus: K-type Thermocouple A thermocouple is a thermoelectric device for measuring temperatures. Thermocouples consist of two wires of different materials, connected at two points called junctions . Due to the difference in the thermal conductivity of the two materials, a small voltage differential is developed at the junction that is proportional to the temperature difference. This voltage is normally in the mV range, and a signal conditioner (read amplifier ) is used to boost this voltage to the voltage range, generally 0-5V. In understanding how the voltage changes with respect to temperature, accurate temperature measurements are made. 1 ENME 471 #1: Linear Heat Conduction

Figure 1: K-type thermocouple This experiment utilizes K-type thermocouples to measure temperatures axially along the solid cylinder. K-type thermocouple refers to a thermocouple containing Chromel and Alumel conductors, and are the most widely used thermocouples due to their robust nature and wide temperature profile. As with all sensors, there is an associated error with the measurement. For a K-type thermocouple, the error is ±0.75% OR ±2.2C, whichever is greater. Thermocouple error must be considered in experimental analysis. Thermocouples have a natural drift in their measurement. Drift occurs due to the changes in the thermoelements during the operation of a thermocouple. The offset associated with the drift of each thermocouple will be provided as a part of analysis under the lab heading in D2L. TD1002A Mkll This experiment is mounted onto the TD1002 Base Unit, and is called TD1002a Mkllm, seen in Figure 3. The experiment consists of a rod surrounded by insulation, heated on one side by an electric heater, and cooled on the hotter by a Thermo Fosher cooling unit, holding the water at 6C. The display is used to set the heating value of the electric heater from 30-100W, as well as read out the temperature data in Celsius. The cross-sectional area of each test article is 0.000707m 2 . Figure 2: TD1002a Mkll Experimental Set Up 2 ENME 471 #1: Linear Heat Conduction

The unit has a interchangeable middle section material that can be one of four materials. There are seven K-type thermocouple probes that are evenly spaced out at a distance of 15mm from one another, sketched in Figure 3. The entire tube section of the experiment is isolated using insulation to reduce heat loss by radiation and convection, reducing error relative to theoretical calculations. Figure 3: Schematic of heated block The experimental set-up has inherent heat loss associated with it due to the spacing between the interchangeable section and the ends. This heat loss is somewhat mitigated using thermal paste, however TecQuipment Ltd provides a heat loss approximation based on the ambient temperature of the experiment. The estimated percent heat loss for the temperature difference measured by the first thermocouple and the ambient temperature is given in Figure 4. Figure 1: Heat Loss Percentage of TD1002a Experiment 3 ENME 471 #1: Linear Heat Conduction

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version