Humidity Independent Control Air Conditioning Research Articles

Performance analysis of a novel dual-evaporation-temperature combined-effect absorption chiller for temperature and humidity independent control air-conditioning

Temperature and humidity independent control (THIC) air-conditioning (AC) systems are promising alternatives to conventional AC systems. A novel dual-evaporation-temperature combined-effect (DETCE) absorption chiller for THIC AC application is proposed. It can produce high-temperature (16–18 °C) and low-temperature (7 °C) chilled water with a thermal coefficient of performance (COP) above 1 by the deep utilization of heat source at around 100–120 °C. Theoretical models were established to investigate effects of generation temperature (Tgen), evaporation temperature and high-temperature cooling capacity ratio (HCR) on thermal performance of the novel chiller. The results show that the COP of the proposed chiller (COPch,prop) is largely affected by Tgen and HCR. The COPch,prop is 24.1 %-50.4 % larger than that of the conventional single-effect absorption chiller (SEABC) under typical HCRs (0.5–0.7). Performance comparison of the DETCE absorption chiller-based THIC AC system and the conventional SEABC-based AC system was also conducted under different room sensible heat ratios (RSHR), fresh air ratios (FR) and ambient conditions. It is found that the proposed system has a greater energy-saving potential when applied in an air-conditioned space with a large RSHR and FR. Under typical RSHRs (0.6–0.8), both the thermal energy saving rate (ESR) and the heating fluid saving rate of the novel system are over 20 %. Besides, the proposed system can achieve an average ESR of around 30 % under a wide range of ambient conditions. This study provides a novel solution for the deep utilization of solar energy or waste heat at around 100–120 °C to achieve efficient and environmentally friendly THIC AC.

Research on thermodynamic performance of a novel building cooling system integrating dew point evaporative cooling, air-carrying energy radiant air conditioning and vacuum membrane-based dehumidification (DAV-cooling system)

In this work, a novel building cooling system is proposed, namely DAV-cooling system, which integrates dew point evaporative cooling, air-carrying energy radiant air conditioning and vacuum membrane-based dehumidification. The DAV-cooling system does not use any organic refrigerants, and can naturally provide fresh air indoors to prevent managers from arbitrarily reducing fresh air, and can be flexibly adjusted to meet different cooling requirements. In addition, the thermodynamic model of the DAV-cooling system is established, and some systematical analysis of parameters of the DAV-cooling system is carried out. The results indicate that there is an optimal ratio of fresh air to primary air for the DAV-cooling system, and the optimal value of this ratio should be in the range of 0.2–0.4. When the DAV-cooling system operates under the condition of a higher flow of primary air, the requirements for the dehumidification efficiency of the vacuum membrane-based dehumidification device can be reduced. Moreover, the relationship between COP and cooling capacity ratio is revealed, and it is found that COP decreases as the cooling capacity ratio increases, but they are not in an absolutely one-to-one relationship. Outdoor temperature and humidity also have a greater impact on the performance of the DAV-cooling system. For Singapore and Changsha in the period from June to August, the COP of the DAV-cooling system is about 5–7 and 4.5–9 respectively when the permeate side pressure is 20 kPa. Finally, the engineering design methods of the DAV-cooling system are discussed, and it is found that the DAV-cooling system can be designed as a temperature and humidity independent control air conditioning system through the proposed design method and the established model. This work can provide a complete solution reference and some new insights for the application of next-generation HVAC systems.

Indian Oil lets contracts for new units at Barauni, Haldia refineries

In this work, a novel building cooling system is proposed, namely DAV-cooling system, which integrates dew point evaporative cooling, air-carrying energy radiant air conditioning and vacuum membrane-based dehumidification. The DAV-cooling system does not use any organic refrigerants, and can naturally provide fresh air indoors to prevent managers from arbitrarily reducing fresh air, and can be flexibly adjusted to meet different cooling requirements. In addition, the thermodynamic model of the DAV-cooling system is established, and some systematical analysis of parameters of the DAV-cooling system is carried out. The results indicate that there is an optimal ratio of fresh air to primary air for the DAV-cooling system, and the optimal value of this ratio should be in the range of 0.2–0.4. When the DAV-cooling system operates under the condition of a higher flow of primary air, the requirements for the dehumidification efficiency of the vacuum membrane-based dehumidification device can be reduced. Moreover, the relationship between COP and cooling capacity ratio is revealed, and it is found that COP decreases as the cooling capacity ratio increases, but they are not in an absolutely one-to-one relationship. Outdoor temperature and humidity also have a greater impact on the performance of the DAV-cooling system. For Singapore and Changsha in the period from June to August, the COP of the DAV-cooling system is about 5–7 and 4.5–9 respectively when the permeate side pressure is 20 kPa. Finally, the engineering design methods of the DAV-cooling system are discussed, and it is found that the DAV-cooling system can be designed as a temperature and humidity independent control air conditioning system through the proposed design method and the established model. This work can provide a complete solution reference and some new insights for the application of next-generation HVAC systems.

Proposal and parametric study of solar absorption/dual compression hybrid refrigeration system for temperature and humidity independent control application

The solar absorption refrigeration technology plays a major role in the building energy saving and emission reduction. According to the concept of energy cascade utilization, this paper proposes a novel solar absorption/dual compression hybrid refrigeration (SADC-HR) system, which consists of solar-driven single effect absorption refrigeration (SSAR) subsystem and power-driven dual-source dual-compression refrigeration (PDCR) subsystem. An air-cooled compression refrigeration (ACR) cycle is integrated with the water-cooled compression refrigeration (WCR) cycle to make up the PDCR subsystem, so as to satisfy the all-weather space cooling/heating demand. The SADC-HR system achieves the cascade production and utilization of cold energy for the temperature and humidity independent control air conditioning system. The thermodynamic model of the SADC-HR system is built to evaluate the system performance and operating parameters, and the comparisons with two conventional systems are also discussed. The results indicate that there are optimum generating temperature of 70 °C and optimum evaporating temperature of 18 °C for the SSAR subsystem to obtain the lowest power consumption at low solar intensity of 450 W/m2. The SADC-HR system also exhibits better economic performance, and its solar collector area is respectively 55.79% and 34.75% lower than that of the conventional SSAR system and solar absorption-compression cascade refrigeration (SA-CCR) system at low solar intensity of 450 W/m2. In addition, the proposed system shows the better energy-saving performance as well as a smaller environmental impact, whose power consumption is reduced by 61.47% compared with the conventional SA-CCR system at solar intensity of 800 W/m2, and the present case study demonstrates that total seasonal electricity consumption in the SADC-HR system decreases a value of 25.32% which corresponds to a decline of 21580.66 kg of CO2 emission in comparison with the conventional ACR system.

Simulation and Analysis of a Novel Cascade Double Cooling Source Temperature and Humidity Independent Control Air-conditioning System

In view of the climate characteristics of hot summer and cold winter area, a novel cascade double cooling source air-conditioning CDCS system is proposed in this paper. The system can achieve heat-humidity independent control in hot and humid summer and high efficiency heating in cold winter. In this paper, theoretical analysis and Aspen Plus simulations are carried out to study the refrigeration of the system under various operating parameters and climatic conditions, meanwhile the comparison between the proposed system and two conventional systems is performed. Results demonstrate that the refrigerating efficiency of the novel system are 52.7% and 22.7% higher than that of the conventional single-cold air-conditioning and dual-cold air-conditioning, under the optimal design parameters.

The Cognition to the Temperature and Humidity Independent Control Air-conditioning System

This thesis introduced the advantages of temperature and humidity independent control air conditioning system compared with traditional air conditioning system and the realization principle of temperature and humidity independent control air conditioning system. Then the thesis introduced the classification of temperature and humidity independent control system and the advantages and disadvantages of each kind of system, and finally summarized the existing problems of temperature and humidity independent control system.

An experimental study on a novel direct expansion based temperature and humidity independent control air conditioning system

Direct expansion (DX) air conditioning (A/C) system are widely used in various buildings because they are simpler and more energy efficient, and generally cost less to own and maintain. However, it is often problematical for a conventional On-Off controlled DX A/C system to simultaneously control indoor temperature and humidity, since the cooling and dehumidification process of air are highly coupled, unless costly extra equipment or complicated control method to decouple the cooling and dehumidification are provided. Therefore, a novel DX based temperature and humidity independent control air conditioning (DX-THIC) system with two parallel-connected condensers and two electronic expansion valves is presented for improved indoor environmental control and energy efficiency. This paper reports on an experimental study on the operating performances of a prototype experimental DX-THIC system. The experimental results demonstrated that the proposed DX-THIC system can provide independent control of indoor temperature and humidity. The experimental results also demonstrated that the indoor air humidity could influence the operating performances of the DX-THIC system.

Analysis on the Utilization of Temperature and Humidity Independent Control Air-conditioning System with Different Fresh-air Handling Methods

The presented research illustrates the characteristics of Temperature and Humidity Independent Control (THIC) system with different fresh-air handling methods through engineering case studies. The investigated methods include dehumidification with the application of cooling, liquid desiccant, dual cooling sources dehumidification and dehumidification wheel. By analyzing the dehumidification processes on psychrometric charts, this study summarized main design focus then conducted detailed calculation for equipment sizing. Furthermore, this study compares energy consumptions for the four methods. Results show liquid desiccant and dual cooling sources dehumidification are more suitable for general office buildings in terms of energy conservation. Dehumidification wheel method consumes too much energy therefore not applicable for comfort air conditioning systems.

Experimental investigation on a novel temperature and humidity independent control air conditioning system – Part II: Heating condition

Air source heat pump is a widely adopted system for winter heating in Central China and South China due to its high energy efficiency and low maintenance cost. However, such systems cannot produce any latent capacity resulting in decreased indoor air quality. Newly developed temperature and humidity independent control system (THIC) provides a solution to this problem. In this study, a novel THIC system was introduced and experimentally investigated under heating condition, which consisted of a solid desiccant heat pump (SDHP) and a variable refrigerant flow (VRF) air conditioning system to handle the latent load and sensible load, respectively. An experimental setup of the joint SDHP and VRF system (JDVS) was established, and the system was evaluated by indoor air condition, energy consumption and system coefficient of performance (COP). In addition, the proposed JDVS system was compared with widely adopted joint heat recovery ventilator (HRV) and VRF system (JHVS). Experimental results show that JDVS can keep indoor humidity ratio at about 50%RH, however JHVS can only increase the indoor humidity ratio to around 30%RH. In addition, JDVS can achieve energy saving of 9.3%, while the COP of JDVS increases by 45.2% compared with JHVS.

Experimental investigation on a novel temperature and humidity independent control air conditioning system – Part I: Cooling condition

Temperature and humidity independent control system (THIC) has become a research focus for its merits of energy saving and improved indoor thermal comfort. In this paper, a novel THIC system was experimentally investigated, which consisted of a solid desiccant heat pump (SDHP) to handle the latent load and a variable refrigerant flow (VRF) air conditioning system to deal with the sensible load, respectively. An experimental setup of this joint SDHP and VRF system (JDVS) was established to measure the system performance under cooling condition. Meanwhile, an experimental setup of widely adopted joint heat recovery ventilator (HRV) and VRF system (JHVS) was also built up to make a comparison. Performances of both JDVS and JHVS were evaluated by indoor air condition, energy consumption and coefficient of performance (COP). Experimental results show that, JDVS can achieve energy saving of 17.2%, while COP of JDVS increases by 25.7% compared with JHVS. In addition, JDVS with indoor relative humidity stabilizing at 50%, can provide better indoor thermal comfort than JHVS.

The Application of Temperature & Humidity Independent Control Air-Conditioning System Based on the Ground Source Heat Pump

The air-conditioning system is discussed in an office building of Yunlong demonstration area, located in the northwest of Zhuzhou city in Hunan province. The climate of Zhuzhou is subtropical monsoon climate and it is highly humid all the year, hot and humid in the summer. The air-conditioning system used the ground source heat pump is the cold and heat source of temperature and humidity independent control system, which has improved the efficiency of the energy use. And the use of the soil thermal energy has improved the energy efficiency of the system.

Research of Temperature and Humidity Independent Control Air-Conditioning System

In this paper, the working principle, relevant equipments and characteristics of temperature and humidity independent control (THIC) air-conditioning system were presented. And authors summarized the application status, design conditions and application conditions of THIC air-conditioning system. Through the research of the system application at home and abroad, authors pointed out the engineering limitations and the way to improve and popularize the technology application.

Application of Temperature and Humidity Independent Control Air-Conditioning System—Using for Winding Workshop of Viscose Filament Production in Coastal Regions

Application of Temperature and Humidity Independent Control Air-Conditioning System—Using for Winding Workshop of Viscose Filament Production in Coastal Regions