Hydronics Offers a Cool, Comfort Advantage New Technology Lowers System Costs
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guest editorial by Greg Cunniff, P.E . Hydronics offers a cool, comfort advantage New technology lowers system costs. ago. Direct evaporative cooling appeared not long afterward. Fresco paintings from ancient Egypt depict slaves waving fans over contain ers of water. This appears to be the earliest re corded use of direct evaporative cooling. Wealthy citizens of Rome during the Ro man Empire had water circulated through their walls. The common people hung wet mats over their doors for cooling. Cooling towers were constructed in medi eval times. The towers were designed to trap wind and funnel it past water before it entered a building. This method is believed have to have been developed in Persia. Water evapo rative cooling was used in New England textile mills during the 1800s. Later this evolved into direct evaporative cooling or swamp coolers, used principally in the Southwest until the early 1960s. With the advent of mechanical cooling, the use of Example of a chilled beam. air conditioning in residences increased dra matically. In the 1960s, less than 30% of new he world we live in would not be the tern can provide the owner or the user of homes were constructed with air conditioning. same if air conditioning weren't avail the system the most comfort for the least Today it is more than 90%. T able. Entire regions of the world would dollars in both first-cost as well as oper Air distribution systems are generally less have remained undeveloped, sustaining mini ating cost, regardless of a building's size, labor intensive to construct. However, they take mal populations. if air conditioning hadn't be configuration or climate setting? up more space and require almost three times come a part of our lives. And beyond cost. is one system better than as much horsepower and three times as much Today air conditioning is rightly consid the other in terms of attainable comfort levels, material to move Btu around a building than a ered a necessity rather than a luxury. A good indoor air quality, energy use, and particu hydronic or refrigerant distribution system. This amount of economic activity, and hence prog larly in matters relating to safety and liabil has a significant impact on the environment in ress. would not have been achieved without ity? This column and future ones will explore higher energy consumption for the building and it. It is one of the key inventions sustaining these issues. an impact on the global environment to mine. modern life. In fact. the Encyclopaedia Britan process and transport more materials to the site nica lists air conditioning as one of the great Comparing systems for the comfort distribution system. est inventions of all time. The three basic methods to provide comfort A building with an all air-duct system can With air conditioning so essential. it helps and move Btu around a building use water. air take up to several feet more in ceiling space to understand how it is provided via mod or refrigerant. then a hydronic or refrigerant distribution sys ern HVAC systems. and what the major dif Air systems have been around for a long tem, resulting in a taller building and again ferences are between the principal delivery time. They were the first systems to provide more materials to construct. systems: hydronics, air and refrigerant or cooling comfort from fans through evaporative Hydronic water systems have long provided direct expansion (DX) systems. Which sys- cooling from a person's skin thousands of years very comfortable and reliable heating and air Note: The views expressed here are strictly those of the author and do not necessarily represent pme or BNP Media. 22 pme 7. 13 guest editorial conditioning, and they come with several major These have typically been smaller split systems load the heat exchanger is oversized for the advantages: excellent indoor comfort (especially for residential and small commercial use. Larger lower mass flow rate since it was sized for with multiple zonesj, lower energy costs and commercial DX systems - variable refrigerant full load and the system is more efficient. improved indoor air quality. Plus, new develop volume (VRVI and variable refrigerant flow (VRFI There is some lower limit for reduced mass ments are occurring with hydronic-based chilled - are now gaining market share. flow and turndown, at which point flow be water systems. The popularity of radiant heat VRF has been called "another refinement of comes laminar and heat transfer decreases. For systems that now include a radiant cooling and DX refrigerant split systems." Unlike earlier ver refrigeration equipment this is somewhere at chilled beam option is growing. The emergence sions of DX refrigerant split systems that em about 25% part load. of new single-pipe systems can dramatically ployed multiple air-cooled condensers matched The HVAC industry is now offering variable lower the usually higher first costs of a hydronic to a single evaporator and refrigerant lines, speed refrigeration equipment for chillers, heat system in comparison to an air or DX system. VRF systems typically use one large condenser, pumps and packaged equipment in addition to New piping materials such as polypropylene one set of refrigerant pipes for the entire build VRF equipment. All this equipment exhibits in are making their appearance, substantially re ing and a separate evaporator for each zone of creases in efficiency at part loads similar to VRF ducing the labor penalty for piping distribution temperature control. This is similar to a hydronic equipment. systems. Technology is available today to sub chilled water system, but with refrigerant pipe. Although the first cost of a typical DX split stantially reduce the amount of pumping en VRF systems have lower cooling energy system is lower than a hydronic distribution ergy for a hydronic distribution system. Using costs than previous constant-speed refrigera system, the first cost of VRF systems are more variable-speed drives will significantly reduce tion equipment because of the variable-speed expensive because of the more complicated re pump energy consumption, as will a single-pipe operation of the compressors. Variable-speed frigerant management system and controls. distribution system. systems of any kind (air, water or refrigerant! Most significantly, VRF systems use refriger Refrigerant or DX systems have been around pump less mass flow resulting in less horse ant a toxic fluid and, in high enough concen a shorter time than air or hydronic systems. power to move the fluid. ln addition, at part trations, a lethal fluid. Mechanical codes have LAARS~ HEATING SYSTEMS The Perfect Choice COMMERCIAL BOILERS, TANKS for Todais Demanding AND WATER HEATERS Applications Laars boilers, volume water and pool heaters are everything a modern heater should be - easy to use, easy on the environment, powerful and compact. Laars has been providing innovative water heating and storage solutions ince 1948 with commercial 0 heaters ranging from 300 to 5,000 MBH at efficiencies from 82 to 95%+. 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With rising en ergy and first costs, there's a need for variable-speed tech nology to provide more attractive returns. A different refrigerant, based on the principle of "wa ter refrigeration," is now being used in Europe. R718, or water vapor, is benign on both the environment and on building occupants but requires an expensive titanium compressor to be able to spin fast enough to achieve the higher pressures. Work on substituting a cheaper carbon fiber plastic for titanium is under way in order to achieve higher efficiency at lower first costs. 6; Moving Btu around a building Jli :; Air systems use a fluid that is nontoxic and readily 3 available: air. However, air systems use a fluid that has ~ An example of installed variable-speed drives. a low specific heat and low density. As a result, it takes cl: 24 pme 7.13 guest editorial more horsepower to move Btu around a build power to move Btu with water vs . air. This technology is being installed here in North ing and distribute them in an occupied space can be as low as 10% to 20% of the total America. With radiant cooling, piping in with air than any other fluid. Air systems electrical demand of a cooling system. stalled in the ceiling has chilled water in can take as much 40% of the total electrical The science and technology behind hy it. Your warm body radiates to the chilled demand, generation and distribution, for a dronics has advanced to the point today ceiling above to cool you down without cooling system just to move Btu. where we can literally distribute Btu with moving air. Radiant cooling is an exciting While VRF refrigerant systems don't take out any air movement. The problem with air feature that avoids some of the challenges as much horsepower to move refrigerant movement from a comfort standpoint is the with space-cooling distribution common to around a building, they still have to dis creation of evaporative cooling- it's uncom both air and refrigerant VRF-types of air tribute the Btu within the occupied space fortable when air is blowing over our bodies.