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Variable displacement compressors have proven to be more energy efficient than the equivalent compressor with fixed displacement for mobile A/C applications. Variable displacement compressors de-stroke rather than cycle to prevent the evaporator from freezing. Cycling an internally controlled variable compressor is counter intuitive, yet results in a 15-20% reduction in the energy used by the compressor as demonstrated by tests on multiple vehicle applications. Externally controlled variable compressors have the highest energy efficiency and extending cycling to these compressors during cool temperatures reduces the compressor energy consumption by 10%.

Air Conditioning systems with reheat reduction based for energy efficiency have generally been implemented with either electronic variable compressors through active stroke control or with fixed displacement compressors through modifying the cycling set point. The present work demonstrates a unique concept of achieving energy efficiency via cycling a pneumatic variable compressor at elevated set points. The energy efficiency of such a system approaches that of an electronic variable but significantly higher than that of a fixed displacement compressor system. The cost of the system, on the other hand, is substantially lower than that of an electronic compressor. Secondary benefits include a softer start than with a fixed compressor and a considerably simpler control scheme than that required by an electronic variable compressor.

Heating and cooling of automotive seats is a relatively new technology that delivers conditioned air to the occupant's seat providing an overall improvement in passenger comfort. This paper combines experimental and computational data to describe the effect of seat heating on passenger comfort. Included are: (1) a review of current seat heating technologies, (2) the introduction of an innovative seat heating technology using the vehicle's HVAC system, (3) the inclusion of thermal comfort seat strategy for improving overall comfort, and (4) validation of the thermal comfort seat strategy with experimental data. The paper focuses on the occupant's overall comfort in heating mode under different ambient conditions.

Heating and cooling automotive seats are a relatively new technology that delivers conditioned air to the occupant's seat providing an overall improvement in occupant comfort. This paper combines experimental and computational data to describe the effect of seat cooling on occupant comfort. Included are (1) a review of current seat cooling technologies, (2) the introduction of an innovative seat cooling technology using the vehicle's HVAC system, (3) the inclusion of thermal comfort seat strategy for improving overall comfort, and (4) validation of the thermal comfort seat strategy with experimental data. The paper focuses on the occupant's overall comfort in cooling mode under different ambient conditions.

The focus of this paper is to understand, from experimental data, the R134a refrigerant emission rates of various hose materials due to permeation. This paper focuses on four main points for hose assembly emission of R134a: (1) characteristics of hose permeation in response to the effect of oil in R134a and the characteristics of hose permeation of vapor vs. liquid refrigerant; (2) conditioning of the hose material over time to reach steady state R134a emission; (3) the relative contribution of hose permeation and coupling emission to the overall hose assembly refrigerant emission; (4) transient emission rates due to transient temperature and pressure conditions. Studies include hoses with different materials and constructions resulting in various levels of R134a permeation.

As automotive power-train systems become more efficient, less waste heat is available for vehicle passenger cabin warming. As a result, alternative heating technologies are being investigated to alleviate this shortcoming. One alternative is to operate the existing A/C system in reverse (heat pump mode), thus providing supplemental heat. Recently, the environmental impact of refrigerant emissions has come under global scrutiny. The concern is their potential for global warming. Thus, the environmental characteristic of merit that makes for a more benign refrigerant in terms of emissions is lower Global Warming Potential (GWP). R-152a is a more environmentally benign refrigerant compared to R-134a with a GWP of 120 vs. 1,300 [1] and [2]. Both refrigerants are hydro-fluorocarbons - HFCs - (contain no chlorine) and hence, have zero ozone depletion potential. An environmentally benign refrigerant touted as a potential replacement for R-134a, is CO2.

In recent years, climate protection has become as important as ozone layer protection was in the late 1980's and early 1990s. Concerns about global warming and climate change have culminated in the Kyoto Protocol, a treaty requiring its signatories to limit their total emission of greenhouse gases to pre-1990 levels by 2008. The inclusion of hydrofluorocarbons (HFCs) as one of the controlled substances in the Kyoto Protocol has increased global scrutiny of the global warming impact of HFC-134a (called R-134a when used as a refrigerant), the current mobile air conditioning refrigerant. Industry's first response was to begin improving current R-134a systems to reduce leakage, reduce charge, and increase system energy efficiency, which in turn reduces tailpipe CO2 emissions. An additional option would be to replace the current R-134a with a refrigerant of lower global warming impact. This paper documents the use of another HFC, R-152a, in a mobile A/C system.