A detailed explanation to elaborate a strategy for an effective selection of its mechanical refrigeration system.
By Mauricio Baena *
Day by day we are faced with the need to make decisions when selecting our different components of the refrigeration system. Several of these questions might be: What kind of compressors used, which system energy saving more makes sense for my system, what type of refrigerant used, how I optimize the use of it in the system, what it is the appropriate technology for this purpose, etc. Finally, we must use tools that allow us to make the best technical-economic decision in our system.
A selection in a refrigeration system may be motivated by one of the following reasons:
1. Fulfill a present need in your plant or market. They are defined requirements, established by a client or work team, where space and usage is already determined.
2. Improve energy consumption. They are opportunities that seek a space, either because of insufficient energy capacity or because the technologies, facilities and operation are inefficient for what is currently available.
3. Balancing the production and marketing systems of your business. Systems incapable of supporting the operation and acting as bottlenecks in the process.
4. Change of technology. Compliance with regulations, systems inoperation, the growth of need are all reasons that lead to a change of technology.
The first thing to determine correctly is the value of the thermal load that my need requires. There are many software that allow you to determine the thermal loads. All of them, by means of algorithms, calculate the thermal load according to a data of feeding or Input Data.
The important thing in this step is not to enter the data, what is important is to review the criterion with which that data is assigned and entered into the software. Particularly I think that although software is a very useful tool, the loads must be carried out step by step, in a spreadsheet, or paper, that allows us to understand the impact of each data in the equation. Once you have criteria, using the software will be more accurate.
After obtaining the load, we proceed to determine the type of system, the refrigerant and the components of the system (compressor, evaporator and condenser), in order to close our range of possibilities. The size of the load allows us to reduce the options in the compression technology and reduces the choice of refrigerants. The application of the equipment (what should I cool and where), limits the options for evaporation, gives me criteria to validate the refrigerant, and gives me criteria to validate the type of system. The location of the system offers me elements to determine the type of refrigerant and type of mechanical system. This process is a flow of decisions that sometimes forces a decision that almost completes the requirements of a project should be reviewed at the end, because it is not the most optimal for the place, for example.
Although there are many variables to consider, the selection process can be simplified by grouping and classifying the variables into three groups:
- Group A: Technical variables. It meets the definition of the mechanical equipment that meets the thermodynamic needs of the cycle. No system should be discarded. The COP (Operability Coefficient) is not the only critical variable in this process. The study of these variables allows us to determine:
- Thermal load.
- Type of system.
- Elements of the refrigeration system.
- Group B: Financial Variables.
- Capital cost.
- Cost of operation.
- Benefits in the productive or commercial process.
- Group C: Locative Variables.
- Location Space.
- Space Required.
Identifying then my need and clearly defining my variables, the flow of decisions is simplified and allows me to concentrate on what is really important:
1. Fulfill a present need in your plant or market. The order of analysis is technical, financial, locative variables. We know exactly what is needed. Conditions of humidity, temperature, air velocity in my refrigeration system are not negotiable.
2. Improve energy consumption. The order of analysis is financial, technical, and locative. First, I must explore if the project has the expected return on investment, evaluating each system solution. But the result of the analysis of the technical variables is the basis of the decision.
3. Balancing the production and marketing systems of your business. The order of analysis is locative, financial, and technical. The problems of flow in the cooling processes are usually associated with space: very close, very withdrawn, little space for cooling time, little space for inventory storage. The analysis of these variables will allow me, together with the financial resources resulting from the increase of efficiency in the system, to adopt the necessary technology for my production process. I place the technology as the last because generally this type of decisions goes in line with the technology that is already installed in my system.
4. Technology Change. The order of analysis is technical, locative, financial. No matter the investment, I require a technology for an inescapable reason, and a technical premise. Then I must carefully review if the technology you apply can be used on the site with the available resource, and finally I must procure the resource, which is the consequence of the previous decisions.
More and more processes force us to become efficient, and more efficient over time. It is vital to know that the implementation of mechanical refrigeration systems requires an interdisciplinary group that analyzes each of the variables. The information and its analysis are simplified and I can get the best result in my investment experience.
* Mauricio Baena is the Director of ICE Andina and MB of Refrigeration Engineering. It can be contact in the email: email@example.com