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Energy efficiency label policy has been implemented worldwide as a means to address the rise in residential carbon emissions resulting from the growing quantity and intensity of air conditioner (AC) usage triggered by climate change. Using data from the China General Social Survey, this study explored whether households that purchased energy-efficient AC (with energy efficiency labels) consumed less electricity and its mechanisms. We find that households purchasing energy-efficient AC consume 17.2% more electricity annually and 21.9% more during the summer compared to those who do not. This effect is particularly pronounced for younger households and those in warmer or hotter regions, but is constrained by older households and those with awareness of energy saving. The reasons are that the purchase of energy-efficient AC changes households’ AC usage behavior under climate change, including increased usage times, lower usage temperatures, and preferred standby settings. The findings above provide useful recommendations for policy formulation in collaboration with energy efficiency labels to reduce carbon emissions while ensuring human welfare under climate change.

An integrated simulation model is developed to investigate the steady-state and dynamic performance of multi-unit air conditioners (MUACs). It is built as two-phase fluid network which is able to describe different systems by incidence matrixes. And the submodels are embedded in the system framework, where the submodels can be either steady-state or dynamic model, distributed parameter or lumped parameter model. For this case, the numerical submodels are employed with moving-boundary models of condenser and evaporator, steady-state models of compressor and electronic expansion valve. The comparison with experimental data shows that it cannot only predict the steady-state performance, but also catch dynamic trends with high accuracy, for example, the differences of evaporating pressure < ± 4%, condensing pressure < ± 3%, compressor discharge temperature < ± 4°C, superheating degree < ± 2°C and subcooling degree < ± 1°C. Therefore, the simulation model is confirmed as an effective tool to analyze the steady and transient characteristics and optimize the design and control algorithm of MUACs.

Energy, environment and economics are considered as very vital parameters for the evaluation of an air conditioning system and associated indoor environment. The cooling performance of an air conditioner has an effect on the thermal comfort of occupants in the room. Transcritical CO₂ air conditioner (System B) with a control for gas cooler pressure has better energy performance than a transcritical CO₂ air conditioner (System A) without any control on the gas cooler pressure. An experimental technique is used for generating performance equations to define transcritical CO₂ air conditioners in the EnergyPlus program. EnergyPlus simulates combined model of a transcritical CO₂ air conditioner and room for known yearly weather data for an effect on thermal comfort in the room. Thermal comfort in the room is evaluated using the Fanger thermal comfort model and the Pierce two node model. The better energy performance of System B results in improved indoor room environment of the room. The total cooling of System B is 15.78–20.2% higher than that of System A. The Fanger thermal comfort model shows that 95% to 133% people are more dissatisfied with an indoor thermal environment during the morning and 85% to 127% people during the afternoon for a room coupled with System A vis-à-vis room with System B.

Fault detection and diagnostics (FDD) can be used to monitor the performance of air conditioners (ACs) and heat pumps (HPs), signal any departure from their optimal performance, and provide diagnostic information indicating a possible fault if degradation of performance occurs. For packaged systems fully assembled in a factory, an FDD module can be fully developed for all units of a given model based on laboratory tests of a single unit. For field-assembled systems, laboratory tests of a representative AC or HP installation can lead to the development of a “back-bone” preliminary FDD algorithm; however, in situ adaptation of these algorithms is required because of installation variations in the field. This paper describes a method for adapting a laboratory-based FDD module to field-assembled systems by automatically customizing the in situ FDD fault-free performance correlations. We validated the developed data-clustering technique with a set of nearly 6000 data points to generate fault-free correlations for an HP operating in the cooling mode in our laboratory. The study evaluated several fault-free feature models and indicated that the use of different order correlations during stages of data collection produced better fits to the data.

This study presents a method for analysing air conditioner efficiency by using a thermal performance curve. Enhancement techniques consisting of the use of a phase change material (PCM), a vapor compression heat pump (VCHP), ultrasound, drop-in refrigerant, a commercial R-32 air conditioner using ultrasound and a double-storage tank are reported under the weather conditions in Thailand. For the PCM, Rubitherm20 (RT-20) in the forms of a paraffin ball and a plastic pack was selected to cool the return air of the evaporator, which directly caused decreases in power consumption of 7.85% and 5.78%, respectively. The R-123 VCHP was integrated with the air conditioner at the condenser to receive and boost rejected heat to the hot water temperature of 60–70^∘C. Ultrasonic wave generators at 42kHz frequency were installed at the evaporator to improve heat transfer characteristics and reduce the electrical power usage of the air conditioner by 8%. The R-32 drop-in refrigerant technique was tested in an R-410a air conditioner model. The R-32 unit showed the advantages of a smaller environmental impact and a higher cooling energy efficiency ratio (EER) compared with that of the R-410a unit. Moreover, the commercial R-32 air conditioner and a 40 kHz ultrasonic generator were integrated. The combined unit revealed a higher EER of 7.69% compared with that of the conventional commercial R-32 unit. For a double-storage tank, it was shown that the maximum hot water temperature in the storage tank was approximately 49^∘C. The highest effective method to enhance the cooling capacity of air-conditioner is the technique of R-32 air conditioner and ultrasonic wave for increasing the cooling efficiency of 8.54%.

This work presents a technique to improve the thermal performance of an R-32 air conditioner by using ultrasonic waves. Two 1-TR air conditioners — one with and one without 40kHz/50W ultrasonic generators — were tested under controlled conditions in a 3.6m $\times 3.6$m $\times 2.5$m room. The air temperature and humidity conditions entering the condenser and evaporator coils were controlled under 12 conditions to mimic the climate of Thailand. The testing results indicated that the average energy efficiency ratio (EER) of the modified ultrasonic R-32 air conditioner unit was 3.685kW_th/kW_e and the normal R-32 unit without the ultrasonic generators was 3.375kW_th/kW_e. The testing conditions also indicated that the cooling efficiency of the modified system could be increased by approximately 7.69%. Moreover, the convective heat transfer coefficient of the modified ultrasonic R-32 unit was approximately 17.36% higher than that of the normal R-32 unit without the ultrasonic generators because the ultrasonic waves could increase the turbulence in the refrigerant flow and decrease the condensed water at the fan coil unit. In terms of economic results, the payback period of the modified unit based on the climate of Thailand ranged from 0.8–1.2 y, leading to a savings in power consumption of approximately 400–620kWh/y.

Disruptive innovation is an effective process of product innovation, and the analysis of disruptive technological opportunities is an entry point of developing disruptive innovative products. Based on the fact that the sub-functions of a product get different degree of attention from customers or engineers, a construct of functional role is introduced and a classification is proposed. According to the definition and characteristics of new market disruptive innovation, functional roles of functions that a product has are adjusted, and an approach to identify some disruptive technological opportunities of mechanical products was proposed. Finally, air conditioner was taken for example, and the generation of disruptive innovative opportunities verifies the feasibility of the approach.