A framework for creating thermal zones in a building for effective and efficient heating ventilation and air conditioning (HVAC) system design is introduced here. This method is based on simple “sort and eliminate” schemes and requires design cooling loads of conditioned spaces obtained from load calculation tools as primary input. The developed methodology is applied for creating thermal zones, determining corresponding supply conditions and ascertaining sizing of a dedicated outdoor air system (DOAS) with local recirculating units. A simulation study on a prototype-building model shows that a DOAS coupled with zoned recirculating systems that serve distinct thermal zones in a building (zoned model) perform comparatively better in controlling both space temperatures and humidity without significantly compromising HVAC energy and chiller loads than un-zoned HVAC systems serving the whole building as a single thermal block (un-zoned model). The consistency in the performance of zoned HVAC systems is verified by applying three different simulation weather files for New Delhi. Better performance along with logical and computational simplicity makes this design procedure a good alternative to traditional methodologies.
Although wrap-around heat pipes (WAHP) are widely used for enhanced dehumidification systems in tropical and hot-humid climates, very few literature resources have actually reported any control methodology applicable for WAHP dehumidifier systems for an entire year’s operation. In the present work, a methodology is proposed for an outdoor air unit equipped with a WAHP-based dehumidifier along with other auxiliary components. For this, the ambient conditions over an entire year are categorized into six constituent regions based on temperature and humidity levels. The proposed method involves defining specific control sequences corresponding to ambient conditions under each psychrometric region for tandem operation of system components. Fundamentally, this establishes a sort of segregated climatic control protocol for maintaining acceptable levels of humidity and temperature inside the conditioned spaces during a whole year’s operations. An energy simulation study is performed for two DOE prototype office buildings with six representative weather locations ranging from extremely hot and humid to dry and hot as per ASHRAE’s climate classification. Results show that a 100% outdoor unit comprising WAHP-based dehumidifier system equipped with proposed climatic controls saves cooling plant energy in a range of 1.5–19%, when compared with a similar WAHP-based outdoor unit without any climatic controls and auxiliary components. The proposed controls also enable the outdoor air unit in maintaining comparatively better indoor environmental conditions (temperature and relative humidity), resulting in lesser number of building occupied hours drifting away from prescribed indoor temperature and relative humidity limits than its basic counterpart without any climatic controls. This substantiates the intent and applicability of proposed control methodology for WAHP-based dehumidifier systems.
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