This is a product development visual walk-through for a D.I.Y. inspired evaporative cooler design that i created for the 2012 spring semester industrial design 3rd Year Product Design Studio at Auburn University, under the knowledgeable guidance and creative support of INDD Instructor, Jerrod Windham. In this visual design blog, I detail the creative process of the cooler design, from initial research of the current mobile cooling market and review of alternative cooling solutions. To conceptual thinking and physical form studies that address internal airflow characteristics and various production ideas required to meet the developed design criteria. To CAD development for technical specifications and assemblage visualization for transfer to a z-axis computer numerically controlled (CNC) machine to route out the vacuum form molds made of layered medium-density fiberboard (MDF). Then to heating of the styrene plastic that is then vacuum formed over the molds to manufacture, close-to-production quality prototype components that assist in the physical study of the sequence of use, interface ideologies, and in preparations for data acquisition of baseline and normal operating values of a sealed, working model prototype evaporative cooler, ultimately establishing and showcasing the overall efficiency of my evaporative cooler design.
Brief Explanation of General Operating Principles of Evaporative Cooling Systems
Evaporative coolers (often called “swamp coolers”) work on the principle of circulating air being drawn through an evaporative pad that has water cascading along the pad surface, capable of lowering the air temperature as effective, yet more energy-efficient at times, than a conventional compressor-type air conditioning units, in more optimal conditions and environmental scenarios. Areas in southwest US and similar dry, arid environments throughout the world show the largest gain from using these type of units. Evaporative cooling systems depend on an internally or externally powered air circulation delivery / carrier systems (i.e. fan) to draw air towards and blow air flow over the cooling media(i.e. evaporative pad). Air must move into contact with the liquid to affect the cooling process. A coolant fluid such as water has an advantage of high volume heat capacity and much higher thermal conductivity compared to air. The heat exchange coefficient for liquid such as water is many times higher than for air, resulting in the possibility for compact and energy efficient cooling system configurations. There are many existing instructions on how to make your own D.I.Y. evaporative cooler using widely available household parts and existing electronic elements found in any local hardware store or home improvement center. The D.I.Y. designs found online are similar in manufacturing / assemblage, and vary either through increased interior volume capacity (i.e. larger containers), numerous intake fan options (i.e. multiple fan orientations, various power and energy consumption classes of fans), many intake opening, placement and pattern variations and different materially manufactured evaporative pads (natural and synthetic), but ultimately all function under the same simple operating principle of: water drips on vertical pad via pump mounted in a reservoir,an air circulation system that both draws air through an evaporative pad medium and redirect it out the cooler system.
Examples of Existing DIY Coolers
Development of a Full-Scale Foam Board Prototype
During the form studies and conceptual thinking processes, i decide to develop a full-scale foam board prototype of the collapsing evaporative cooler design to physically interact with the sequence of use, review proportional design elements, and address non-operational storage/transportation (long-term / short-term).
Initial Thoughts on Current Design Approach and Discovery of a New Focus
In the ultimate search for a rugged design that can withstand extended period uses and possible military applications, I opt to reformulate the design using the least amount of moving parts, and give further consideration to the various manufacturing options and uncertain possible stability issues that i found with the foam prototype form study of the expandable design concept (seen above). I come up with a refined concept direction that I ultimately journey down, due to finding a mind-blowing amount of information that brings forth issues of material logistics (i.e. non-efficient use of energy) that compressor-type cooling systems currently established by our military forces in dry, arid desert-like areas of operation. The military is using modern home air conditioning units that use refrigeration compressors to cool down our forward deployed troops, to keep them nourished and promote a better quality of life in remote, distant outposts and military installations. The Iraq/Afghanistan operational budget for just cooling of troop tents is well recorded and established at 20.2 billion dollars annually (a NPR 2011 report, among many others), which includes more than just the cost of the cooling unit itself, it includes fuel cost, fuel delivery to remote locations, professional installation and maintenance, and spraying of a thick polyurethane foam to insulate the already outdated tents, to prevent escapement of the conditioned air inside. The new design (seen below) is an approach to a solution that without a doubt, as post data research establishes, will decrease and possibly cut, substantially, a large portion of the 20.2 billion dollar annual cost for the current military cooling infrastructure in place.
Final Cooler Design Concept Sketch
Key Refined Concept Details and General Design Solutions
— Used a simplified manufactured-minded design, utilizing no moving, expanding/collapsing elements to potentially fail over time through material fatigue and improper storage/use, which creates ease of general unit maintenance over time.
— Dual pad intake design allows for oncoming wind to be drawn from one intake and the generally square design of the cooler itself creates a type of pressure drag that arises because of the blunt-faced form and large apparent cross-section, thus it provides a higher drag coefficient on the opposite side. (vortex type effect as wind is channeled around the side of the unit, and swirls into the rear intake due to the absence of any aerodynamic streamlining, feeding the non-wind facing intake.
— Capable of stacking (by post/beam/pole strapping) multiple units to one vertical mounting structure for conditioning of large spaces (i.e. medical tent, dining tent, multi-use spaces that are commonly occupied by large groups of individuals at one time.
— The cooler unit(s) can be strapped (via the center strap tunnel / ratchet strap system) to an existing and/or self-prepared pole, post, tree, frame, wall, etc. to provide an elevated fixed location to draw in fresh air from unspoiled air currents above clustered tent formations and to further avoid kick-up of dirt and/or sand from vehicular or troop movements in the immediate area of cooler operation.
— The “V” shaped recess design on the main body panels, is purely a observation that a round form resting on a flat plane is not stationary along the vertical axises under outside pressures and forces (i.e. wind gusts and compression pressure from ratchet strap mounting system) compared to a round form resting in a notched “valley-like” shape, providing more security and control with two points of material contact. The “V” shaped form allows for a snug, secure resting location for any circular shaped pole, post, beam, tree / or a flat faced post /structure (i.e. a 4×4 wooden post, square tubing) with a diameter of 20″ and smaller.(well within the range of commonly available pole, post, beam and indigenous tree diameters commonly found or acquired through supply / surplus and construction divisions found throughout most large, long-term / extended stay military installations)
— Incorporated a rubber bumper-type system to prevent damage to exterior structure during elevated mounting, during both flat faced mounting and “V” notch post mounting options.-
– Integrated systems (fan, pump, intake feed systems, various piping and bracketing) use strength enhancing mounting locations that ensure added rigidity for the outer case itself and improved vibration resistance, and longevity of the motor driven hardware inside. (ex. support bracket for mounting the fan system is at the same time, the same rigidity enhancing bracing that is used for improved structural integrity of the outer case assemblies); allows for manufacturing of fewer, yet more robust multi-structural supporting, multi-integrated components, respectively reducing required inventory stock and ease of maintenance and general repair through simplification of the assembly requirements.
Begin to address design issues and create solutions to work out the finer points of the cooler design such as fastening technology options, material tolerances and the internally incorporated, strength improving support/mounting structural core.
Satisfied with design details, i move forward into setting up cut files for the Z-Axis CNC machine to start routing out the various 3/4″ layered MDF molds to be used for vacuum forming of the final working cooler parts / panels / elements.
Stay tuned for more updates as i continue to move forward with the development of this cooler design and begin to sort through the initial atmospheric data gathered that will begin to lay the groundwork for what may lead to further development to improve interior airflow draw and delivery as well as possible alternative powered subsystems (i.e. solar panels) to try to achieve maximum cooling capacity through smart and conscience use of a renewable energy source.