Open top display cooler - energy loss

• ttj
In summary, the conversation discusses an energy analysis in a supermarket and the challenge of calculating energy usage for open top display coolers. The speaker mentions using a program called Coolpack which identifies air infiltration as the main issue. The conversation also suggests various ideas for measuring and reducing energy usage in open front supermarket display refrigerators. The conversation ends with a recommendation to use a clamp on ammeter and a link to an article discussing the physics of grocery store display cases.

Homework Statement

I am working on a energy analysis in a supermarket. There is some open top display coolers, which is using a lot of energy - I don't have the opportunity to check excatly how much energy they use, so I have to calculate it. I don't 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 going to 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 :)

Homework 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:
A google image search, "supermarket open display refrigerator"

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.