Post on 23-Dec-2015
transcript
SOLAR WATER HEATER
This presentation deals with solar water heaters.
There are two categories (passive, active)
There are two common types (conventional, vacuum tubes); uncommon - reflective
Any of these may operate on one of two principles : direct or heat exchange.
objective
A B
C D
CXC CSEC PHYSICS SYLLABUSSECTION C : THERMAL PHYSICS AND KINETIC THEORY
Objective 4.6 b : Students should be able to relate the principle of thermal energy transfer to the design of devices – solar water heater.
Our Focus : Conventional passive direct. Pre-requisite : (a) Thermal transfer
( b) Absorption of radiation lesson
Conduction
(solids) Convection
(fluids)Radiation
(vacuum)
Flat black
objects
PASSIVE : ACTIVE
Passive : Outlet from collector is lower than inlet of hot water inlet to storage tank.No pump required.
Active : Outlet from collector is higher than hot water inlet to storage tank.Pump required.
More passive
More active
EXAMPLES OF PASSIVE
To active slide
EXAMPLES OF ACTIVE
CONVENTIONAL : VACUUM TUBE
More conventional
More vacuum tubes
CONVENTIONAL
To vacuum tubes
MORE VACUUM TUBE
REFLECTIVE
DIRECT : HEAT EXCHANGE
OUR FOCUS : CONVENTIONAL PASSIVE DIRECT
DETAILS OF HOW IT WORKS
A : How heat reaches Earth from SunB : Why the glass?C : Copper tubes with heat sinks, painted flat black.D1 – D2 : Collector slanted with outlet at upper end and inlet at lower end.E : Insulated storage tank.F : Hot water outlet from tank to house at top of tank.
critical thinking
CRITICAL THINKING
State two correct features of the above diagram and one bad feature.
Please pause the video now, think about this for a few minutes, and then continue to find out how your answers compare with mine.
DO YOU THINK THIS SYSTEM WILL WORK?
questions
Please pause the video now, think about this for a few minutes, and then continue to find out how your answers compare with mine.
QUESTIONS: 1: By what method does heat from the sun reach
Earth? Radiation 2. What effect does the glass of the collector
produce? Greenhouse effect 3. Why is everything in the collector painted flat
back? Flat black – best absorber of infrared radiation 4. What is the process by which heat is
transferred through the walls of the copper tubing? Conduction
More questions
QUESTIONS 5. In the passive system, by what process does
the water flow through the tubes and into the storage tank?
Convection 6. Why would 4 mm PVC (plastic) be a better
material for the inside of the storage tank than 1 mm steel (assuming that both have the required strength)?
4 mm PVC is a better insulator. 7. Why is the hot water pipe to the home
connected to the top of the storage tank? The hot water, being less dense, floats at the top.
passive
resources
RESOURCES:
http://www.energysavers.gov/your_home/water_heating/index.cfm/mytopic=12850
http://www.builditsolar.com/Projects/WaterHeating/water_heating.htm
http://chinasolarwaterheater.blog.com/working-principle-of-solar-water-heater.html/
http://www.motherearthnews.com/Renewable-Energy/1979-09-01/A-Homemade-Solar-Water-Heater.aspx
http://www.youtube.com/watch?v=oBpKPes3cEE
passive
Conventional passive
Please visit http://csecphysics.weebly.com to view this presentation and to download a copy of the accompanying brochure or this PowerPoint presentation. To take the quiz, you will need an access code (available to my students).
EXAMPLES OF PASSIVE
To active slide
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