Test Review April 24, 2009 DRILL Get with a partner and go over your solutions to the 3G and 3H Test Review. Pay particular attention to #9 on the Fluid Technology side. You have ~12 minutes.

(Fluid and Thermal Technology) Test Review TEST FRIDAY – Unit 3G and Unit 3H (Fluid and Thermal Technology)

Test Review Solutions Define the following Thermal Technology – the technology of producing, storing, controlling, transmitting and getting work from heat energy. Thermodynamics - the science dealing with internal energy, heat, and work Photon – a particle of light Conduction – the transfer of heat through a substance by collision of molecules. Convection – is the transfer of heat by movement of a fluid. Radiation – the transfer of energy by electromagnetic waves.

Test Review Test Review Solutions List 3 example of Thermal Technologies and identify why they are considered a thermal technology. Example applications: Furnace, Hot water heater, Toaster, Insulation, Heat exchanger, Refrigerator, Hot air balloon, Fan, Engine cooling system, Oven, Blow-dryer, Thermos, Heat shrink, Styrofoam, Radiator, Blanket, Winter jacket, Wool socks…

Test Review Test Review Solutions What is the purpose of using infrared photography if hot objects are often red to our eyes? The more powerful radiation heat is in the form of infrared light, which we cannot see with our natural eyes. Therefore, infrared photography allows us to “see” the heat given off by objects even if the material is not hot enough for there to be a color change.

Test Review Solutions Natural Convection Forced Convection What are the two types of convection? Explain each. Natural Convection Fluid surrounding a heat source receives heat and rises (due to lower density) Surrounding cooler fluid moves in to replace it. Cooler fluid is heated, rises, and cycle continues. Forced Convection Fans or other means are used to propel a fluid. An convection current is induced. Car engine and A/C are examples

Test Review Solutions Yellow Red White Blue Orange 3 1 5 4 2 Number the following from 1-5, 1 being coolest and 5 being hottest. Yellow Red White Blue Orange 3 1 5 4 2

Test Review Test Review Solutions (Solid / Liquid / No Medium) is the medium for conduction. (Solid / Liquid / No Medium) is the medium for convection. (Solid / Liquid / No Medium) is the medium for radiation. Thermal energy always travels from a region of __________________ temperature to a region of __________________ temperature. The driving force for heat transfer is ______________________________________________ The more accurate way of saying an object is “cold” is saying that it ____________ heat. The three methods of heat transfer are ____________________________________________. The sun’s heat reaching us through space is an example of the method of _____________________. Higher Lower Temperature Difference (Difference of Temperature) Lacks Convection, Conduction, Radiation Radiation

Test Review Test Review Solutions A car engine cooling system is an example of the method of _____________________. Heat from a house in winter travels through the walls by the method of _____________________. Give an example of a technology that combines chemicals to produce heat: ___________________. Give an example of a technology that converts mechanical energy to heat: ___________________. Give an example of a technology that converts electrical energy to heat: ___________________. Give an example of a technology that converts light energy to heat: ___________________. Sketch an example of Conduction, Convection, and Radiation: Convection Conduction Heat Pads Car Engine / Basketball Electric Stove Incandescent Light Bulb

Test Review Test Review Solutions What must be constant for Boyle’s Law to be usable? _______________________ Using gas to apply force or to transport is a particular type of fluid technology called _____________________. Using a liquid to apply force or to transport is a particular type of fluid technology called _________________. Why is aerodynamics considered fluid technology? What are two things that fluid systems have in common? Temperature Pneumatics Hydraulics Aerodynamics deals with the motion of air and other gaseous fluids and with the forces those fluids have on objects. 1) Fluids 2) A pressure difference

Test Review Test Review Solutions Show mathematically why you would rather someone push against you with 10 lbs. of force on a 50 square inches piece of wood than with a 0.0031 square inch pinhead. (Hint: calculate the pressure of each) Write given information: F = 10 lbs A1 = 50 in2 A2 = 0.0031 in2 P1 = ? P2 = ? Write formula and solve: P1 = F1 / A1 P2 = F2 / A2 = (10 lbs) / (50 in2 ) = (10 lbs) / (0.0031 in2 ) P1 = 0.2 psi P1 = 3225.8 psi I would rather someone use a block of wood since the pressure is MUCH less.

(Inversely Proportional) Test Review Test Review Solutions Based on what we covered in the Fluid Technology unit, there are at least two ways to correctly label the axes of each of the graphs below. Do so. P or V P or V V or P 1/V or 1/P (Inversely Proportional) (Proportional)

Test Review Solutions V 1 / P or [Volume is proportional to 1/P] There are two ways to mathematically express the relationship between volume and pressure. Do so and explain. (Hint: Pressure and volume are inversely proportional.) V 1 / P or P 1 / V [Volume is proportional to 1/P] a [Pressure is proportional to 1/V] a

Test Review Test Review Solutions On a separate sheet of paper write three new, different problems related to fluid technology. Use your previous problem sheet for examples. One problem should require use of the basic P = F / A formula. One problem should be a simple Boyle’s Law problem. One problem should use the diagram below. After writing these three problems, solve them.

Test Review CLASSWORK/HOMEWORK With a partner, identify 3 examples of Conduction, Convection, and Radiation (total 9 examples) not discussed in class. Describe your observations of the heat transfer in each example. Describe what is causing the heat transfer in each example.