Residential Air Conditioning Research Articles

Performance of a Split-Type Air Conditioner with Natural Refrigerant R1270 to Replace R22

A natural and environment friendly refrigerant propylene (R1270) is proposed as a substitute of R22 in the residential air conditioner. The experiments on the cooling performance of the air conditioner with R1270 and R22 were respectively conducted on an existing enthalpy potential bench, during the degree of superheating keep constant and refrigerant charge directly on the conditioner, also the effect on system performance in the condensing temperature was tested, it is founded that the cooling capacity of R1270 air conditioner was 96% that of R22 air conditioner while the COP of the former increased, and the refrigerant charge amount of R1270 was 56.8 % lower than R22.

Numerical Simulation of Operating Performance of Heat Exchangers in a Residential Split Air-Conditioner

The mechanism of fluid flow and heat transfer in the heat exchangers was investigated in this paper. Using R22 as the working fluid, the steady distributed parameter models of condenser and evaporator in a residential split air-conditioner were established based on thermophysical laws such as mass, momentum and energy conservation equations. The regions of two-phase fluid and superheated gas in evaporator and the regions of superheated gas, two-phase fluid and subcooled liquid in condenser were respectively simulated under designed conditions of air-conditioning system. Based on the calculated results, the flow and heat transfer performances of heat exchangers were analyzed. The results show that the two-phase fluid regions in both evaporator and condenser have great influence on the fluid flow and heat transfer performances in it.

Compensation of flow maldistribution in fin-and-tube evaporators for residential air-conditioning

Compensation of flow maldistribution in multi-channel fin-and-tube evaporators for residential air-conditioning is investigated by numerical modeling. The considered sources of maldistribution are distribution of the liquid and vapor phases in the distributor and non-uniform airflow distribution. Fin-and-tube heat exchangers usually have a predefined circuitry, however, the evaporator model is simplified to have straight tubes, in order to perform a generic investigation. The compensation of flow maldistribution is performed by control of the superheat in the individual channels. Furthermore, the effect of combinations of individual maldistribution sources is investigated for different evaporator sizes and outdoor temperatures. It is shown that a decrease in cooling capacity and coefficient of performance by flow maldistribution can be compensated by the control of individual channel superheat. Alternatively, a larger evaporator may be used.

Optimal replacement of residential air conditioning equipment to minimize energy, greenhouse gas emissions, and consumer cost in the US

A life cycle optimization of the replacement of residential central air conditioners (CACs) was conducted in order to identify replacement schedules that minimized three separate objectives: life cycle energy consumption, greenhouse gas (GHG) emissions, and consumer cost. The analysis was conducted for the time period of 1985–2025 for Ann Arbor, MI and San Antonio, TX. Using annual sales-weighted efficiencies of residential CAC equipment, the tradeoff between potential operational savings and the burdens of producing new, more efficient equipment was evaluated. The optimal replacement schedule for each objective was identified for each location and service scenario. In general, minimizing energy consumption required frequent replacement (4–12 replacements), minimizing GHG required fewer replacements (2–5 replacements), and minimizing cost required the fewest replacements (1–3 replacements) over the time horizon. Scenario analysis of different federal efficiency standards, regional standards, and Energy Star purchases were conducted to quantify each policy's impact. For example, a 16 SEER regional standard in Texas was shown to either reduce primary energy consumption 13%, GHGs emissions by 11%, or cost by 6–7% when performing optimal replacement of CACs from 2005 or before. The results also indicate that proper servicing should be a higher priority than optimal replacement to minimize environmental burdens.

Cars are buildings: Building-like energy use in automobiles

This paper examines vehicle energy use as if vehicles were buildings. Vehicle air conditioners are much less efficient than residential air conditioners, and in the US consume about 0.9 quadrillion BTUs (quads) per year, comparable to the 2.3 by air conditioners in residences. Vehicle heating, in contrast, is a model of efficiency, running as a combined-heat-and-power system using waste heat from the motor. Electricity use from appliances such as DVD players, laptops, and refrigerators remains modest, although stand-by power use is growing. Technology and policy approaches used for buildings can address similar types of energy use in cars.

Air conditioning in the region of Madrid, Spain: An approach to electricity consumption, economics and CO2 emissions

An understanding of electricity consumption due to residential air conditioning (AC) may improve production and environmental impact strategy design. This article reports on a study of peak and seasonal electricity consumption for residential air conditioning in the region of Madrid, Spain. Consumption was assessed by simulating the operation of AC units at the outdoor summer temperature characteristics of central Spain. AC unit performance when operating under part load conditions in keeping with weather conditions was also studied to find cooling demand and energy efficiency. Likewise final electricity consumption was computed and used to calculate energy costs and greenhouse gas emissions (GHGs). Cooling demand, when family holidays outside the region were factored into the calculations, came to 1.46 × 10 9 kWh. Associated seasonal electricity demand was 617 × 10 6 kWh and seasonal performance of AC units around 2.4. Electricity consumption in the whole region was observed to peak on 30 June 2008 at 5.44 × 10 6 kW, being the load attributable to residential AC 1.79 × 10 6 kW, resulting about 33% of the total peak consumption. The seasonal cost per household was about €156 and the total equivalent warming impact was 572 × 10 3 t CO 2 . The method proposed can be adapted for use in other regions. ► The residential demand of AC in the Region of Madrid is studied including the effect of family seasonal holidays. ► A simulation of the air-cooled mechanical compression cycle was performed and several results were obtained such as a seasonal COP of 2.4. ► Some air-cooled AC apparatus marketed were studied and a “Commercial COP” was obtained. ► Electricity consumption and equivalent CO 2 emissions were also assessed and the seasonal COP was compared with commercial COP. ► Finally, influence of residential AC on electricity consumption of the whole region is analyzed, including also consumption peaks.

Performance of residential air-conditioning systems with flow maldistribution in fin-and-tube evaporators

Refrigerant and airflow maldistribution in fin-and-tube evaporators for residential air-conditioning was investigated with numerical modeling. Fin-and-tube heat exchangers usually have a pre-defined circuitry. However, the objective in this study was to perform a generic investigation of each individual maldistribution source in an independent manner. Therefore, the evaporator and the condenser were simplified to be straight tubes for the purposes of this study. The numerical model of the R410A system, its verification and an investigation of individual maldistribution sources are presented in this paper. The maldistribution sources of interest were: inlet liquid/vapor phase distribution, feeder tube bending and airflow distribution. The results show that maldistribution reduced the cooling capacity and the coefficient of performance of the system. In particular, different phase distribution and non-uniform airflow distribution reduced the performance significantly. Different feeder tube bendings only caused a minor decrease in performance.

Swimming pools as heat sinks for air conditioners: Model design and experimental validation for natural thermal behavior of the pool

Swimming pools as thermal sinks for air conditioners could save approximately 40% on peak cooling power and 30% of overall cooling energy, compared to standard residential air conditioning. Heat dissipation from pools in semi-arid climates with large diurnal temperature shifts is such that pool heating and space cooling may occur concurrently; in which case heat rejected from cooling equipment could directly displace pool heating energy, while also improving space cooling efficiency. The performance of such a system relies on the natural temperature regulation of swimming pools governed by evaporative and convective heat exchange with the air, radiative heat exchange with the sky, and conductive heat exchange with the ground. This paper describes and validates a model that uses meteorological data to accurately predict the hourly temperature of a swimming pool to within 1.1 °C maximum error over the period of observation. A thorough review of literature guided our choice of the most appropriate set of equations to describe the natural mass and energy exchange between a swimming pool and the environment. Monitoring of a pool in Davis, CA, was used to confirm the resulting simulations. Comparison of predicted and observed pool temperature for all hours over a 56 day experimental period shows an R-squared relatedness of 0.967.

Use of nanoparticles to make mineral oil lubricants feasible for use in a residential air conditioner employing hydro-fluorocarbons refrigerants

The application of nano-fluids in refrigerating systems is considered to be a potential way to improve the energy efficiency and reliability of HVAC&R facilities and to make economic the use of environment-friendly refrigerants. In this paper, we report a method that uses nanoparticles to enhance the energy efficiency of retrofitted residential air conditioners (RAC) employing HFCs as alternative refrigerants. The reliability and performance of RAC with nanoparticles in the working fluid have been investigated experimentally. A new mineral-based nano-refrigeration oil (MNRO), formed by blending some nanoparticles (NiFe 2O 4) into naphthene based oil B32, was employed in the RAC using R410a as refrigerant. A method showing how to disperse the NiFe 2O 4 nanoparticles in the mineral oil refrigeration lubricants is presented together with an investigation of their stability. The solubilities of the new MNRO in R134a, R407C, R410a and R425a were measured. The performances of the RAC, such as the cooling/heating capacity, the power input and the energy efficiency ratio, were determined. The results indicate that the mixture of R410a/MNRO works normally in the RAC. The cooling/heating EER of the RAC increased about 6% by replacing the Polyol-Easter oil VG 32 lubricant with MNRO.

Performance of R170/R1270 mixture under air-conditioning and heat pumping conditions

In this study, the performance of R170/R1270 mixture was measured on a heat pump bench tester to substitute for R22. The tester was equipped with a hermetic compressor providing a nominal capacity of 3.5 kW. All tests were conducted under typical summer and winter conditions of 7/45°C and −7/41°C in the evaporator and condenser, respectively. During the tests, the composition of R170 varied from 0 to 10% with an interval of 2% for the R170/R1270 mixture. Test results showed that the capacities of the R1270 and R170/R1270 mixtures were 3.2–10.0% and 4.2–20.4% higher than those of R22, respectively. The coefficient of performance (COP) of R1270 was 2.7–3.6% higher than that of R22. On the other hand, the COP of R170/R1270 mixture decreased at a constant rate as R170 was added to R1270. The COP of R170/R1270 mixture was similar to that of R22 at 2% R170 and then became lower than those of R22 as R170 increased. For the mixture, the compressor discharge temperature was 8–20°C lower than that of R22. The amount of charge was reduced up to 55% compared with R22. Overall, pure propylene and R170/R1270 mixtures are good long-term candidates from the viewpoint of energy efficiency and greenhouse warming to replace R22 in residential air-conditioners and heat pumps.

열펌프의 고장감지 및 진단시스템 구축을 위한 실시간 정상상태 진단기법 개발

고장감지 및 진단 시스템의 구축의 기초 연구로 정상상태 진단기에 대한 연구를 수행하였다. 정상상태에 대한 진단은 시스템 전체를 관찰하거나 몇몇 필요한 시스템 파라미터를 모니터링 함으로써 가능하다. 최적화된 정상상태 진단기를 이용하면 시스템에서 필수적인 정상운전 시의 기준모델 FDD (no fault reference model)을 자가학습을 통하여 적용할 수 있다. 본 연구에서는 가정용 열펌프가 냉방조건으로 작동할 경우에 대해 이동창을 기반으로 개의 측정값들에 대한 표준편차를 분석함으로써 정상상태 판정을 내리도록 하였다. 정상상태 진단기의 작동의 여부는 실내부하를 조절함으로써 확인하였다. 본 연구를 통하여 열펌프 등의 증기압축 사이클 시스템에 대하여 이동창을 기반으로 한 정상상태 진단기 개발 방법을 제시하였다.

CALCULATION METHOD OF COP OF RESIDENTIAL AIR CONDITIONER BASED ON MEASUREMENT

This research is aimed to propose the method of calculating COP of the residential air conditioner, and to clarify an energy conservation performance and the best operation method. Because the information on the performance of residential air conditioners that we can obtain is usually limited, we propose the calculation method of COP which can be predicted from general catalog information. First, the change in the refrigerating cycle by the outside temperature and the amount of the heat supply was analyzed. Next, the characteristic of COP change was clarified by the theoretic refrigerating cycle COP. Finally, we led the prediction method of COP based on the similarity of the relation between power consumption and the heat supply.

Technology of Noise Reduction for Residential Air Conditioner

Technology of Noise Reduction for Residential Air Conditioner

Orbiting compressor for residential air-conditioners

A new type of compressor, called an orbiting compressor, is introduced in this paper. The orbiting compressor is characterized by an orbiting piston, and the piston or orbiter consists of a circular base plate and a ring type vane protruding vertically from the base plate. The orbiter is made to orbit in an annular space formed between two concentric circular walls via an Oldham-ring mechanism, producing two sealed gas pockets on both sides of the vane wrap with a 180° phase difference. This operating mechanism leads to alternating compression and discharge processes, which results in low torque variation. The orbiting compressor has been designed for an R410A residential air conditioner with a cooling capacity of 10.0 kW. The performance of the orbiting compressor model has been analytically investigated, where the volumetric, adiabatic and mechanical efficiencies were calculated to be 94.8%, 90.4% and 93.4%, respectively for the ARI condition. The EER was estimated to be about 10.86 with a motor efficiency of 89%.

Performance of heat pumps charged with R170/R290 mixture

In this study, thermodynamic performance of R170/R290 mixture is measured on a heat pump bench tester in an attempt to substitute R22. The bench tester is equipped with a commercial hermetic rotary compressor providing a nominal capacity of 3.5 kW. All tests are conducted under the summer cooling and winter heating conditions of 7/45 °C and −7/41 °C in the evaporator and condenser, respectively. During the tests, the composition in R170/R290 mixture is varied from 0% to 10% with an interval of 2%. Test results show that the coefficient of performance (COP) and capacity of R290 are up to 15.4% higher and 7.5% lower, respectively than those of R22 for two conditions. For R170/R290 mixture, the COP decreases and the capacity increases with an increase in the composition of R170. The mixture of R170/R290 mixture at 4%/96% composition shows the similar capacity and COP as those of R22. For the mixture, the compressor discharge temperature is 17–28 °C lower than that of R22. For R170/R290 mixture, there is no problem with mineral oil since the mixture is composed of hydrocarbons. The amount of charge is reduced up to 58% as compared to R22. Overall, R170/R290 mixture is a good long term ‘drop-in’ candidate from the view point of energy efficiency and greenhouse warming to replace R22 in residential air-conditioners and heat pumps.

Overall Thermal Transfer Value of Residential Buildings in Malaysia

This study presents the Overall Thermal Transfer Value (OTTV) and the energy consumption of room air conditioners of the residential buildings in Malaysia. A survey has been conducted to investigate the OTTV and the energy consumption of room air conditioners of the residential buildings in Malaysia. OTTV calculation, energy consumption and effect of the building parameters on energy consumption have been investigated. It is found that OTTV of the residential buildings in Malaysia varied from 35 to 65 W m -2 with a mean value of 41.7 W m -2. The sensitivities of several parameters such as window to wall ratio (WWR), Shading Coefficient (SC), U-value for wall (U w) and solar absorption (I±) are provided to design and optimize the thermal performance of residential buildings. It is found that U and I± influence more on OTTV compared to other parameters. The analysis shows that about 14, 10 and 5 of residential building air conditioners have annual electricity consumption in the ranges 500 to 1000 kWh, 1000 to 2000 kWh and 7500 to 10000 kWh, respectively. The maximum, minimum and average annual electricity consumption of the air conditioner of residential buildings is 22055.5, 136.1 and 3708.8 kWh, respectively. © 2009 Asian Network for Scientific Inform

A ‘drop-in’ refrigerant R431A for replacing HCFC22 in residential air-conditioners and heat pumps

In this study, thermodynamic performance of R431A and HCFC22 is measured in a heat pump bench tester under air-conditioning and heat pumping conditions. R431A is an near azeotropic mixture composed of 71% propane and 29% HFC152a by mass. It has no ozone depletion potential and low greenhouse warming potential of 43. R431A also offers a similar vapor pressure to that of HCFC22 for possible ‘drop-in’ replacement. Test results showed that the coefficient of performance of R431A is 3.5–3.8% higher than that of HCFC22 while the capacity of R431A is very similar to that of HCFC22 under both conditions. The compressor discharge temperature of R431A is 21.1–27.3 °C lower than that of HCFC22 while the amount of charge for R431A is 50.0–51.9% lower than that of HCFC22 due to its low density. Overall, R431A is a good long term environmentally friendly ‘drop-in’ alternative to replace HCFC22 in residential air-conditioners and heat pumps due to its excellent thermodynamic and environmental properties.

Comparison of adsorption systems using natural gas fired fuel cell as heat source, for residential air conditioning

This article aims to evaluate the performances of an adsorption system driven thanks to the heat rejected by the post-combustion exhaust gases of a reformer/fuel cell system for residential air-conditioning application. Three adsorption pairs were compared: activated carbon/methanol, silica gel/water and zeolite/water. Taking into account both cooling power and sensitivity to performances of the heat rejection and recovery exchangers, it appears that zeolite 13X/water is the adsorption pair giving the best performance for this application. Nevertheless, a more detailed model would be of interest to better quantify the heat transfer impact on performance.

Drop-in Test of Microchannel Evaporators Using R-22 for Residential Air Conditioners

The drop-in test of microchannel evaporators using R-22 for residential air conditioners was conducted. Five prototype microchannel evaporators were manufactured and tested in psychrometric calorimeter test facilities. Each evaporator was made with two parallel flow heat exchangers connected with several return pipes. The parallel flow heat exchanger had 41 microchannel tubes with eight rectangular ports. Performance comparisons were made between microchannel evaporators with and without hydrophilic coating to assess the effect on condensate on evaporator surface. Also, various performances of prototype microchannel evaporators were presented. Note that the cooling capacities of prototype 2, with a flow area ratio of 73/58%, and prototype 3, with six return pipes, were larger than prototype 1 by 15% and 9%, respectively. The cooling capacity of prototype 4 with three rows was larger than prototype 1 by 14%. Both refrigerant-side and air-side pressure drops for prototype 2 with the best cooling capacity were 29 kPa and 2.5 mmAq, which are acceptable for residential air conditioners.

Fan with reduced noise generation

Axial flow fan propellers are provided with a roughened portion along the trailing edge of the fan blades on the pressure side of the blade to minimize tonal acoustic emissions generated by laminar boundary layer vortex shedding. The roughened portion may be provided by trip surfaces formed in the blades, by strips of abrasive material adhered to the blades along the trailing edges, respectively, by parallel or cross-hatched serrations in the blades or by upturned or offset trailing edges of the blades. The height of the roughened portion should be about equal to the boundary layer thickness of air flowing over the blade surfaces during operation of the fan. The fan propellers are particularly advantageous in heat exchanger applications, such as residential air conditioning system condenser units.