Analyzing the climatic conditions of design means obtaining important results to execute a project recognizing different levels of demand.
by Ing. Fabio Clavijo *
Background: The selection of climatic conditions in a project is the first step in the process of evaluating thermal loads of a building and at this stage should be analyzed both the technical level of the project and the type of application.
This first step of definitions allows to assure the validity and reliability of the project of air conditioning or refrigeration in the useful life of the project and from there many calculations arise that are going to allow to advance later in the selection of the equipment that will attend each and every one of the technical requirements of a project.
Criteria appear in this process that allow to recognize design conditions not only for the year, but for the different seasons or months of rain, heat or cold that have very different characteristics than those reported in northern and southern areas that tend to present patterns and cycles Very similar annuals, however, in this Torrid Zone, climatic manifestations must be studied with different criteria and patterns of energy consumption that are particular to this region of the world.
Thermal requirement criteria
Recognizing that each project has different levels of technical requirement constitutes a first step of technical definitions and with this the number of annual hours that the project could support under conditions that exceed the design requirements is established.
If we talk about cooling processes for air conditioning, it is very likely that in a shopping center, exceeding the design limits during 2% of annual hours (175 hours) does not constitute a risk for its operation, however, in a laboratory this could mean operational risks and economic losses. For this reason, spaces of critical operating conditions should be considered with criteria of 0.4% (35 annual hours).
Office spaces, on the other hand, are considered spaces of medium level of demand and treated with criteria of 1% (88 annual hours).
The most demanding operating conditions that a system must face are associated with the critical application of a system.
It is established that when considering cooling systems in air conditioning applications, the most demanding design condition is precisely the condition of higher temperature (Dry Bulb) exterior associated with its coinciding wet bulb temperature.
In turn, a project with high demand of low humidity (dehumidification) should consider the external conditions from the highest moisture content (humidity rat) reported by the climate studies, and its corresponding temperature (dry bulb) coincident.
The values studied to support CVR engineering studies (air conditioning, ventilation and refrigeration) are heating, cooling, dehumidification, humidification, evaporation and enthalpy.
To obtain reliable design information, studies are accepted from minimum records of ten (10) consecutive years taken hour by hour, daily, with the support of certified meteorological stations, which we know are available at the airports of each population.
In the study carried out in Colombia by ACAIRE, and under the direction of Eng. Fabio Clavijo, the objective was to expand climate information for sixteen (16) cities, following the methodology established by ASHRAE - American Society of Heating Engineers, Refrigeration and Air conditioner.
This research work provides a new advance and objective of similar studies carried out by ASHRAE that reports climatic conditions for five (5) Colombian cities, as well as previous studies carried out by ACAIRE in years 2004 and 1987, and by the extinct SCMH (Service Colombian Meteorology and Hydrology) in 1971.
Design climatic conditions
Obtained the information by agreement with the IDEAM - Institute of Hydrology, Meteorology and Environmental Studies of Colombia - for the sixteen selected cities, it proceeded to perform the validation of the information obtained by statistical methods and then the readiness to perform the processing of the information , for which purpose, formulation stages were followed to complete the database of psychometric variables of the data, to advance later with the percentile study for the set of variables, applications and levels of technical demand.
The research work, as expected, is supported by the need to document in a structured manner the relevant climate information for the design of CVR systems and also in the need to recognize the climatic behavior that is particular to the Torrid zone.
A third contribution of these studies leads to revise building criteria and building systems in Colombia, and by extension in the Torrid Zone, that support national policies and regulations to provide comfortable and efficient constructions in the energy-environment.
It is clear that each climate zone requires efforts and constructive technical decisions that provide improved levels of energy-environmental performance, which is achieved through energy modeling exercises for different materials and construction methods.
In turn, the climate base of cities is based on data on temperature, humidity, speed and wind direction, for which purpose it is necessary to have hourly data reflecting average conditions for each hour of a typical year. Precisely this task requires historical data of the characteristics of those already developed, so the next step will be to integrate a team to develop this information for each of the cities studied.
Construction systems of buildings
It follows from the foregoing that there is still the task of specifying and advancing research projects that establish minimum acceptable criteria of materials and construction methods of buildings for this region of the world.
These minimum criteria are based on optimized energy consumption, the use of bioclimatic climate control opportunities and the adoption of CVR systems with low environmental impact and reduction of the carbon footprint.
Energy modeling processes will allow the results to be consistently documented, which will be an important contribution to the engineering and architecture of the country and the tropical countries.
The project included projection analysis of maximum and minimum temperatures, by linear projection methods, which allowed estimating global warming trends for these Colombian cities with a time horizon of twenty-five (25) years.
The results show projected increases of maximum temperature, for Bogotá, higher than 0.2 ° C every five years, while the minimum temperatures show decreases of 0.6 ° C in that same period. The net result of climate change is 0.8 ° C every five years, which marks with concern the overflow of this phenomenon.
These results invite, not only to become aware, but to take action to contribute efforts and achieve concrete results that reduce this accelerated process of desertification facing the world.
The media and governments are participating in these efforts to this day, but it is clear that these are too insufficient to make a real change in trend.
There is only one way left. Rethink these efforts and integrate them vertically in society.
The coming generations are grateful for the opportunity to provide them with a stable and progressive society.
* Ing. Fabio Clavijo. President of Tecnaire Ltda. President of the ASHRAE Colombia Chapter. Life member ASHRAE. Ex-President and honorary member of ACAIRE. Lecturer, researcher and author of several books and technical documents. firstname.lastname@example.org