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Homework Help: Open top display cooler - energy loss

  1. Nov 6, 2011 #1

    ttj

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    1. The problem statement, all variables and given/known data
    I am working on a energy analysis in a supermarket. There is some open top display coolers, which is using alot of energy - I dont have the opportunity to check excatly how much energy they use, so I have to calculate it. I dont have problems in calculating it when it is closed, but I have no clue on how to do it, when there is a "open 'wall'".
    I know there are some uncertain variables, temperature, humidity and ventilation. But I'm gonna make them constant:
    Temp outside 22 degr C, humidity outside 50%, temp in cooler 2 degr C, humidity in cooler 85%.

    I have been using the program called Coolpack (EESCooltools), and it is telling me, that my problem is the air infiltration! And I do agree :)

    2. Relevant equations
    The heat loss caused by infiltration can be calculated as

    Hi = cp ρ n V (ti - to) (8)

    where

    Hi = heat loss infiltration (W)

    cp = specific heat capacity of air (J/kg/K)

    ρ = density of air (kg/m3)

    n = number of air shifts, how many times the air is replaced in the room per second (1/s) (0.5 1/hr = 1.4 10-4 1/s as a rule of thumb)

    V = volume of room (m3)

    ti = inside air temperature (oC)

    to = outside air temperature (oC)

    Sources ^^ = http://www.engineeringtoolbox.com/heat-loss-buildings-d_113.html

    Would it be possible to measure the windspeed in the cooler with a anemometer. Then check the speed every 3 cm from the products to the top, and so multiply it by the cross-section and breadth and take the average?


    My other idea is to measure the temperature 10 cm above the products and then: 1) Create a frame of flamingo, cover it with a lid of acrylic 2) Measure the temperature here and then find the difference between an open and a closed.


    All ideas will be appreciated, thanks in advance.
     
    Last edited: Nov 6, 2011
  2. jcsd
  3. Nov 6, 2011 #2
    A google image search, "supermarket open display refrigerator"

    https://www.google.com/search?hl=en...&um=1&ie=UTF-8&tbm=isch&source=og&sa=N&tab=wi

    Came up with,

    http://kaixue.en.alibaba.com/product/489461622-212510680/supermarket_open_display_cooler_showcase.html [Broken]

    Which gives size and power usage half way down the link above.

    What you need is a clamp on ammeter with a time analyzer if such a tool exists.

    See also google search,

    https://www.google.com/webhp?hl=en#...w.,cf.osb&fp=577f5846657ec0b7&biw=734&bih=439

    which turns up,

    http://www.washington.edu/news/arti...of-grocery-store-display-cases-to-save-energy
     
    Last edited by a moderator: May 5, 2017
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