Ye Yao

Experimental study on physiological responses and thermal comfort under various ambient temperatures.

This study mainly explored the thermal comfort from the perspective of physiology. Three physiological parameters, including skin temperature (local and mean), electrocardiograph (ECG) and electroencephalogram (EEG), were investigated to see how they responded to the ambient temperature and how they were related to the thermal comfort sensation. A total of four ambient temperatures (21 degrees C, 24 degrees C, 26 degrees C and 29 degrees C) were created, while the other thermal conditions including the air velocity (about 0.05+/-0.01 m/s) and the air humidity (about 60+/-5 m/s) were kept as stable as possible throughout the experiments. Twenty healthy students were tested with questionnaire investigation under those thermal environments. The statistical analysis shows that the skin temperature (local and mean), the ratio of LF(norm) to HF(norm) of ECG and the global relative power of the different EEG frequency bands will be sensitive to the ambient temperatures and the thermal sensations of the subjects. It is suggested that the three physiological parameters should be considered all together in the future study of thermal comfort.

Energy consumption analysis on a dedicated outdoor air system with rotary desiccant wheel

Abstract A dedicated outdoor air system (DOAS) with rotary desiccant wheel is the combination of a desiccant dehumidification system and a vapor compression refrigeration system. An energy consumption model of this hybrid DOAS is established for its analysis. Coefficient of performance, COP, is appropriately defined for evaluation on performance of the hybrid DOAS. The results indicate that, compared with a conventional DOAS, energy savings are possible for the suggested DOAS, when solar energy or natural gas is used for regeneration. Ventilation air flow rate, temperature or humidity of outdoor air, as well as regeneration-to-process air ratio, influence the energy consumption and the COP of the hybrid DOAS, greatly.

Experimental Study on Skin Temperature and Thermal Comfort of the Human Body in a Recumbent Posture under Uniform Thermal Environments

Experiments are conducted on human subjects to study the overall and the local thermal sensation and thermal comfort as well as the skin temperature distribution of the body in a recumbent posture under different environmental temperatures (21, 24, 26, and 29°C). Local skin temperatures are measured and 14 methods for the mean skin temperature overall are investigated. Statistical analysis showed that the Burton (3 points) method wiu obtain similar results for mean skin temperature compared with the other methods, e.g., Colin/Houdas (10 points), Hardy/DuBois (12 points), Stolwijk/Hardy (unweighted 10 points), and Mitchell/ Wyndham (unweighted 15 points), and is employed in this study due to its simplicity and convenience. Meanwhile, the relationship between skin temperature and thermal comfort and sensation is investigated and overall/local thermal sensation models based on the skin temperature are established according to the experimental data in this study.

Dynamic Modeling of HVAC System with State-Space Method

The design of an efficient HVAC controller that maintains an anticipated indoor thermal environment at minimum energy consumption largely depends on the availability of a valid dynamic model of the system. This paper presents a state-space-based dynamic model for a HVAC system whose components are mainly air-to-water surface heat exchangers, air-supply ducts and water pipes. Firstly, the dynamic models for the components are developed according to the principle of energy and mass conservation. By introducing the vector–matrix notation, the ordinary differential equations describing the component dynamics are converted into the state-space form. Then, the state-space model for the whole HVAC system is developed based on the component models and model connection algorithms. Afterward, experiments have been performed to verify the HVAC system state-space model in predicting the transient responses of exit air temperature and humidity as well as outlet water temperature of the surface heat exchanger under inlet perturbations. The proposed modeling procedure can be especially useful for the development of the dynamic toolbox for the control design of HVAC system.