Dr. David A. Yashar

Dr. David A. Yashar is a mechanical engineer in the HVAC&R Equipment Performance Group of the Energy and Environment Division (EED) of the Engineering Laboratory (EL) at the National Institute of Standards and Technology (NIST). Dr. Yashar's research focuses on making HVAC&R equipment more efficient, intelligent, and reliable. He received his MS degree from the University of Illinois, where his work focused on characterizing and predicting refrigerant void fraction during evaporation. Upon completion of his master’s research, he joined the HVAC&R Equipment Performance Group (formerly the Thermal Machinery Group) at NIST. After beginning his NIST appointment, he simultaneously began working towards his Ph.D. at the University of Maryland. There he worked with NIST and the Maryland Microfluidics Laboratory (MML) to develop a microfabricated fluid control device capable of metering refrigerant expansion.

Dr. Yashar's current research focuses on the characterization of air flow distributions through residential and commercial finned-tube heat exchangers. Through collaborations with the US Department of Energy (DOE), the Air-Conditioning, Heating, and Refrigeration Institute (AHRI), and various manufacturers, he is performing extensive laboratory experiments using Particle Image Velocimetry (PIV) to measure air flow distributions through finned-tube coils in various installation configurations. This research uncovered details demonstrating that certain features commonly built into these coils can cause large sectional variation in air flow, and may include coil portions which are air-starved and therefore incapable of transferring heat. Simultaneously, Dr. Yashar has refined CFD modeling techniques to predict the air flow distributions of the coils examined in the laboratory.

In addition, Dr. Yashar is actively working with Dr. Domanski and members from George Mason University’s Machine Learning and Inference Laboratory to establish a computational tool for the design of evaporators and condensers. This tool is an evolutionary algorithm based program called Intelligent System for Heat Exchanger Design (ISHED) which optimizes the performance of finned-tube heat exchangers for their operating conditions and incident air flow distribution. ISHED is bundled with version 3.0 of EVAP COND, simulation models for finned-tube heat exchangers, and will be released in 2010.

Dr. Yashar started working with the US DOE's Office of Energy Efficiency and Renewable Energy, focusing on household refrigerators and freezers, when he joined NIST in 1998. To this effort, Dr. Yashar regularly assists DOE with refrigerator energy testing anomalies, test waivers, and general consulting related to domestic refrigeration. He has worked with ISO, ANSI, and AHAM groups concerned with domestic refrigerator and freezer test procedures, and he is presently serving as an Expert member to the International Electrotechnical Commission (IEC) SC59M to develop a globally acceptable test procedure for domestic refrigerating appliances. He is also the Chair of ASHRAE Technical Committee 8.9, domestic refrigerators and food freezers, and serves as the Chair of the Standards Subcommittee for the same group.

Dr. Yashar served as the Secretary for the 3rd International Institute of Refrigeration (IIR) Conference on Thermophysical Properties and Transfer Processes of Refrigerants. This conference was the 3rd in a series of conferences hosted by IIR Commission B1, Thermodynamics and Transfer Processes, and takes place every four years.

Dr. Yashar has worked on incorporating MicroElectroMechanical Systems (MEMS) into the HVAC&R industry. In conjunction with his work at the University of Maryland, he devised a modified LIGA-like UV lithography SU8 fabrication method, and used it to prototype a fluid control device. The prototype was demonstrated as a refrigerant expansion device and as a metering device for high pressure gases.