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Radon gas is the most deadly indoor air pollutant. In the US, it is responsible for over 20,000 deaths per year. Residential exposure is typically the largest portion of a person’s annual exposure, so a great deal of research has been done to understand the pathways that radon can follow to enter a house. Since radon emanates from the ground, it is present in high concentration in soil gas. Recent research on the vapor intrusion of volatile organic compounds from subsurface sources into a test house concluded that the sewer line is an important preferential pathway. Despite the potential for …

Air cooled condensers are commonly used in rooftop units and residential air-conditioners to reject heat outdoors. Airborne particles in the environment, such as dust, grass, leaves, seeds, and anthropogenic agents, can foul the air side of the condensers. Therefore, it is common practice to regularly clean the air side of condensers. Seven fouled wavy fin, and two fouled spine fin condensers from residential condensing units were collected at the end of their service lives, and examined in the laboratory to study the effect of the fouling on heat transfer capacity and air-side flow resistance. A test apparatus was designed and …

Refrigeration systems can undergo many faults that could negatively affect their operation and performance. This paper describes a modeling process to simulate the fault impacts on the operation of a commercial walk-in freezer using semi-empirical models. These models often require less modeling effort than full forward models and could be used in scenarios where detailed information is missing, such as in field-measured systems. An important characteristic of a typical walk-in refrigeration system is the existence of a liquid-line receiver after the condenser, which significantly changes the behavior of the cycle, in comparison to a receiver-less system. Component models described in …

Deposition of airside fouling on condensers degrades performance of air conditioning units. Several researchers have studied airside fouling effects on performance of heat exchangers, but much of the work focuses on evaporators. ASHRAE RP-1705, currently in progress, is intended to study condenser air-side fouling, and to characterize fouling material so that realistic fouling could be applied in laboratory measurements. Nine field-fouled split system condensing units have been collected, and fouling samples from two US locations have been collected and analyzed. A test apparatus was designed and built to study the heat transfer and air-side pressure drop through different coils before …

The effects of several types of faults on air conditioners and heat pumps have been studied in many laboratory experiments. All available data have been gathered, and the independent

variable (fault intensity) and each of the dependent variables (fault impacts) are normalized to show the trends in a generalized fashion. Relationships are provided wherever there are sufficient results. Most of the significant fault types are included (except refrigerant charge variation, which was discussed in Mehrabi and Yuill (2017)): condenser heat transfer (CA), evaporator heat transfer (EA), liquid line restriction (LL), compressor leakage (VL), and noncondensables in the refrigerant (NC). Relationships …