Introduction to Engineering: Mechanical T HERMODYNAMICS & E NERGY Created by The North Carolina School of Science and Math.The North Carolina School of Science and Math Copyright North Carolina Department of Public Instruction.North Carolina Department of Public Instruction Created by The North Carolina School of Science and Math.The North Carolina School of Science and Math Copyright North Carolina Department of Public Instruction.North Carolina Department of Public Instruction

Thermodynamics is the study of the connection between heat and work and the conversion of one into the other. Applications: Internal combustion engines Refrigerators HVAC systems Steam Power Plants W HAT IS T HERMODYNAMICS ? By Duk (Own work) [GFDL ( or CC- BY-SA-3.0 ( via Wikimedia Commons

K EY T ERMS Energy – ability to do work. Work – amount of energy transferred by a force exerted over a distance. Heat – a transfer of energy due to thermal contact Temperature – a relative term reflecting how vigorously the atoms of a substance are moving and colliding. Efficiency – the percentage of energy converted into work

U NITS OF H EAT Calorie The amount of heat required to raise the temperature of one gram of water 1 o C. Joule 4.184J of heat energy is required to raise the temperature of one gram of water from 0 o C to 1 o C. 1 J (Joule) = BTU BTU (British Thermal Unit) The amount of energy needed to heat one pound of water one degree Fahrenheit

T YPES OF E NERGY Mechanical Kinetic Potential Sound Thermal Chemical Electromagnetic Electrical Nuclear Energy

M ECHANICAL E NERGY E XAMPLES Potential Kinetic By Stefan Scheer (Own work) [CC-BY-SA ( via Wikimedia Commons By Thierry from Le Plessis Robinson, France (Thunder of Zeus) [CC-BY-2.0 ( via Wikimedia Commons

E LECTROMAGNETIC, C HEMICAL, AND T HERMAL E NERGY E XAMPLES Electromagnetic EnergyChemical EnergyThermal Energy See Notes for photo attributions

E LECTRICAL AND N UCLEAR E NERGY E XAMPLES Electrical Nuclear See notes for photo attributions

W HAT TYPE OF ENERGY IS SHOWN BELOW ? Chemical Energy Image from: “Wagon Lane Park Bench” by Flickr user philwhin Creative Commons CC BY 2.0/

W HAT TYPES OF ENERGY ARE SHOWN BELOW ? Electrical, Mechanical, and Electromagnetic Remote control photo by Flickr user espensorvik Creative Commons CC BY 2.0

H EAT T RANSFER The transition of thermal energy from a hotter to a cooler object Forms: conduction, convection, and radiation. Conduction and convection refer to transfer of thermal energy. Radiation is a conversion of energy to a different form.

Conduction, Convection, Radiation

C ONDUCTION The "diffusion" of thermal energy (heat) through a substance, which occurs because of a temperature gradient Metals are excellent conductors of heat energy, whereas things like wood or plastics are not good conductors of heat. Those that are not so good conductors are called insulators.

C ONVECTION The transfer of heat energy by the movement of a substance, such as a heated gas or liquid from one place to another. Example: hot air rising to the ceiling There are two major types of convection: Forced convection Natural (Free) convection

R ADIATION Radiation refers the transfer of heat energy through empty space. The source of this radiation is the thermal energy of the materials Example: standing in front of a fireplace