Air-Chiller temperature setpoint Parte 2 - Zone Air Temperature fluctuations

asked 2023-10-07 04:50:23 -0600

Zakaria's avatar

updated 2023-10-31 03:36:14 -0600

Hello community members,

I'm currently working on modeling a walk-in freezer (3L x 4W x 2.7H) using EnergyPlus and specifically utilizing the Refrigeration: AirChiller object, based on the RefrigeratedWarehouse example. In my simulation, I aimed to set the temperature control using "the temperature difference between cutout and setpoint" in the "zone control thermostat" object -as suggested by @Boranian - to achieve the desired temperature range (-21°C/-18°C).

However, I've noticed that the modeled temperature fluctuations are occurring at a higher frequency compared to the experimental results, as illustrated in the attached the figure below. For instance, the experimental data shows a single On/Off cycle, while the simulation displays three On/Off cycles within the same time frame.

I suspect that the refrigeration system might be overdimensioned, leading to the rapid temperature decrease in the modeled results.

I'm seeking advice on how to address this issue and ensure that the refrigeration system in the model to better align with experimental data.

What should I do? What parameters should I check or change? Any insights or suggestions would be greatly appreciated!

Thank you in advance for your assistance!


Link to question PARTE1

Walk-in freezer characteristics

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Comparison between experimental and simulated results

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It could be an internal mass issue, have you checked that your constuctions and areas represent your stored products correctly?

Petros Dalavouras's avatar Petros Dalavouras  ( 2023-11-01 01:34:46 -0600 )edit

Thank you for your comment. I didn't quite understand it, however, there are no products stored inside a cold room. It is a simple cold room construction with the refrigeration system mentioned above, in which I have used the Air-chiller object, and the walls construction is made of 200 mm of high density expanded polystyrene foam.

Zakaria's avatar Zakaria  ( 2023-11-28 06:15:10 -0600 )edit

What is the use of the cold room? I figured that since the temperature is -21°C/-18°C that it is used as a freezer for products e.g. food. Is the cold room also empty in you experimental data?

Petros Dalavouras's avatar Petros Dalavouras  ( 2023-11-28 06:55:20 -0600 )edit

The results come from a paper found here. In that paper, they measured the temperature in an empty cold room (Freezer A). As you mentioned, the cold room is meant for storing goods. The plan is to create a model for the cold room that functions well. After that, I'll use a co-simulation approach to model the stored products.

Zakaria's avatar Zakaria  ( 2023-11-28 14:50:35 -0600 )edit

I don't think that the freezer is empty according to this paper. Taken from the paper: "The temperature fluctuation during the normal operation is minimum and its effect on the storage food can be neglected" Moreover, the paper is about the effect of temperature variation on ice cream recrystallization, so why would the freezer be empty in the experimental data?

Petros Dalavouras's avatar Petros Dalavouras  ( 2023-11-29 01:54:55 -0600 )edit