Watts hr BTU eer

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Watts hr BTU eer Powered By Docstoc
					http://physics.colorado.edu/phys3070
           Judah Levine
            JILA S-460
    Judah.Levine@colorado.edu
       303 492-7785 (2-7785)
      M,F 11-Noon, W 1-3 pm
       also by appointment


                             Judah Levine, 3070L14 1
 Refrigerator Energy Flow

              Refrigerator transfers heat
     TH
              From the inside to the room.
              Room warms up by QH
              Refrigerator cools off by QL
QH            QH=QL+W > QL
          W
QL

                    QL BTU / hr
              eer =   =
     TL             W   Watts

                                  Judah Levine, 3070L14 2
 Energy Efficiency Ratio
                   QL BTU / hr
             eer =   =
                   W   Watts

    Suppose eer=13 (a high-efficiency value).

       Typical room air conditioner removes
           12,000 BTU/hr (“1 ton” unit)

       Input power= 12,000/13= 923 Watts

Energy used in 1 day= 923Watts×24hours= 22.2kWh
              $2.22/day @ $0.10/kwh

              Is this a lot or a little?

                                              Judah Levine, 3070L14 3
 Clicker question ..



A: This is a lot
B: Get a life, this is a little




                              Judah Levine, 3070L14 4
            Energy Efficiency Ratio
                                   QL
                    eer (ratio) =
                                   W
                                   BTU / hr
                    eer ( store) =
                                    Watts
Suppose eer(store)=13

How much energy (in joules) does it take to move 10 joules of energy
from the cooler region to the warmer region?

A:   1.31 joules
B:   2.62 joules
C:   10.2 joules
D:   13.3 joules
                                                     Judah Levine, 3070L14 5
Energy Efficiency Ratio
                         BTU / hr
       eer ( store) = 13
                          Watts


        BTU / hr        1watt
eer ≈ 13          ×                = 3.81
          Watts     3.41BTU / hr
               QL
energy ratio =     = 3.81
               W
     QL 10 joules
W=      =            = 2.62 joules
    eer      3.81

                Answer is B

                                            Judah Levine, 3070L14 6
      Heat Pump Energy Flow
QH = W + QL > W                 Room warms up
      QH               TH       by QH
COP =    >1
      W
                  QH
                            W

                  QL


                                 Extract energy QL
                       TL        from the great
                                 outdoors


                                         Judah Levine, 3070L14 7
                        Refrigerator
Evaporates at cold temp             Easy to liquefy

     Cool (inside)                 Warm (outside)
                Gas flow




        Gas
                                     Compressor
                              QL     Gas to liquid                        QH
       Liquid      Expansion
                   valve

                Liquid flow



                                                Judah Levine, 3070L14 8
                     Refrigerants
       F
                         Fluorine/Chlorine replace
Cl    C         Cl       hydrogen in methane
                         structure

       F

     Freon 12




                                               Judah Levine, 3070L14 9
                     Refrigerants
        F
                                  H             F

Cl      C       Cl           F    C             C     F

                                  F             H
        F
     Freon 12                         HFC-134

     CF2Cl2                           CHF2 – CHF2



       Chlorine primarily responsible for ozone depletion



                                                    Judah Levine, 3070L14 10
  Electric power generation

                                       Co
             o il C       O3                il B
         C




                      N            S


    O2
                                                          O1
3-phase
“Delta”                   Coil A


                                             Judah Levine, 3070L14 11
3-phase Delta transmission




                      Judah Levine, 3070L14 12
   Electrical circuit parameters
              joules
Volts = v =
              charge
                     charge
current = amps = i =
                     second
                     joule charge   joule
Volts × amps = vi =       ×       =       = watts
                    charge second second
energy loss = i 2 r
r in ohms

  Energy transfer/work requires motion of charges


                                                    Judah Levine, 3070L14 13
Transmission efficiency
  power delivered = v × i
 transmission loss = i 2 r
 p = 1200 watts
 v = 120volts
    1200
 i=       = 10amps
     120
 r = 1 ohm
 loss = 10 2 ×1 = 100 watts
              output 1200
 efficiency =       =     = 92%
              input 1300

                                  Judah Levine, 3070L14 14
Transmission efficiency
    power delivered = v × i
    transmission loss = i 2 r
    p = 1200 watts
    v = 240volts
    r = 1 ohm
    efficiency =
          A: 88%
          B: 92%
          C: 96%
          D: 98%
          E: 100%

                                Judah Levine, 3070L14 15
Transmission efficiency
  power delivered = v × i
 transmission loss = i 2 r
 p = 1200 watts
 v = 240volts
    1200
 i=       = 5amps
     240
 r = 1 ohm
 loss = 52 ×1 = 25watts
              output 1200
 efficiency =       =     = 98%
              input 1225
                                  Answer= D
                                   Judah Levine, 3070L14 16
High Voltage transmission




                     Judah Levine, 3070L14 17
Step-down transformer

               Step up and
               Step down
               possible only with
               alternating current
               systems




                       Judah Levine, 3070L14 18
   Alternating vs. Direct current

                   Extra credit study:

                  “War of the currents”

                    Thomas Edison
                          vs.
         Nikola Tesla and George Westinghouse


1 paragraph min, 1 page max by Wednesday, 8 March, 9 am



                                                Judah Levine, 3070L14 19
        Light as a wave
Wavelength= distance between wave crests
1 micron=10-6 m
1 nano-meter=1nm=10-9 m

X-rays, gamma rays, …
< 400 nm ultra-violet

400 nm blue
500 nm green
670 nm red

> 700 nm near infrared
>1000 nm = 1micron= far infrared
cm – km: microwaves, TV, FM, AM …


                                           Judah Levine, 3070L14 20
   A Black Body


Absorbs all radiation that falls on it

Kinetic energy of atoms radiates
electromagnetic energy

What is spectrum of the radiation?




                                         Judah Levine, 3070L14 21

				
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