Research on Energy-Saving Performance of Intermittent Heating for Rooms in Hot Summer&ColdWinter Zone

In the hot summer&cold winter zone in China,intermittent heating space for rooms is widely used.However,in comparison with continuous space heating,the energy-saving performance of intermittent space heating has not been sufficiently investigated.This paper studied the factors influencing the energy performance of intermittent heating for the representativeoffice inhot summer&coldwinter zone.Basedon theheatbalancemethod,adynamic thermalmodel of the intermittent heating roomwas built and tested by experiments.And then,it analyzed the total space heating load,the amount of energy saving and energy saving ratio of the intermittent heating under different preheating hours,occupation hours,required roomtemperatures,air change rates,overall heat transfer coefficients(U-value)of windows and wall materials.If the adjacent rooms were not heated,for a typical room occupied about 10 h a day,the energy-saving ratio of intermittent heating was about 30%compared with continuous heating.But the preheating power was higher than two times of continuous heating.The results also indicated that the occupation hours had a significant effect on energy saving amount and ratio,it should be noted that the energy saving ratio by intermittent heating was much lower than the unoccupied period ratio.Relative to other factors,the heating temperatures,room air change rates and U-value of windows,and room envelope materials had little effect on energy efficiency.If the adjacent rooms were heated in the same manner as the roomin question,the energy-saving ratio of the total load of intermittent heating was heavily reduced to 8.46%.

Application of Geothermal Energy to New Countryside Construction——A Case Study of Xiong County, Hebei Province

Hujiatai Village, Xiong County, Hebei Province was nominated as the experimental unit of new countryside construction by Hebei Province in 2008. In order to make Hujiatai Village become a new countryside model with friendly ecological and environmental conditions, local energy resources should be considered. In this study, a mode of 'geothermal energy extraction-heat exchange-space heating-reinjection' was adopted to supply heat to resident houses in Hujiatai Village cooperating with a geothermal development entity based on the abundant geothermal resources, thereby constructing a clean, economic and autarkic new countryside energy system, which avoids utilization of fossil-energy, reduces emission of greenhouse gases and generation of solid coal cinder, protecting air and land environment, improving life quality of the people and building a typical model for Hebei Province and even for the whole country.

Comparison of space cooling/heating load under non-uniform indoor environment with convective heat gain/loss from envelope

The indoor parameters are generally non-uniform distributed.Consequently,it is important to study the space cooling/heating load oriented to local requirements.Though the influence of indoor set point,heat sources,and ambient temperature of convective thermal boundary on cooling/heating load has been investigated in the uniform environment in previous research,the influence of these factors,particularly the convective heat gain/loss through a building envelope,on cooling/heating load of non-uniform environment has not yet been investigated.Therefore,based on the explicit expression of indoor temperature under the convective boundary condition,the expression of space cooling/heating load with convective heat transfer from the building envelope is derived and compared through case studies.The results can be summarized as follows.(1)The convective heat transferred through the building envelope is significantly related to the airflow patterns:the heating load in the case with ceiling supply air,where the supply air has a smaller contribution to the local zone,is 24%higher than that in the case with bottom supply air.(2)The degree of influence from each thermal boundary to the local zone of space cooling cases is close to that of a uniform environment,while the influence of each factor,particularly that of supply air,is non-uniformly distributed in space heating.(3)It is possible to enhance the influence of supply air and heat source with a reasonable airflow pattern to reduce the space heating load.In general,the findings of this study can be used to guide the energy savings of rooms with non-uniform environments for space cooling/heating.

Experimental and Numerical Analysis of a PCM-Integrated Roof for Higher Thermal Performance of Buildings

Phase change materials(PCMs) designate materials able to store latent heat.PCMs change state from solid to liquid over a defined temperature range.This process is reversible and can be used for thermo-technical purposes.The present paper aims to study the thermal performance of an inorganic eutectic PCM integrated into the rooftop slab of a test room and analyze its potential for building thermal management.The experiment is conducted in two test rooms in Antofagasta(Chile) during summer,fall,and winter.The PCM is integrated into the rooftop of the first test room,while the roof panel of the second room is a sealed air cavity.The work introduces a numerical model,which is built using the finite difference method and used to simulate the rooms' thermal behavior.Several thermal simulations of the PCM room are performed for other Chilean locations to evaluate and compare the capability of the PCM panel to store latent heat thermal energy in different climates.Results show that the indoor temperature of the PCM room in Antofagasta varies only 21.1℃±10.6℃,while the one of the air-panel room varies 28.3℃±18.5℃.Under the experiment's conditions,the PCM room's indoor temperature observes smoother diurnal fluctuations,with lower maximum and higher minimum indoor temperatures than that of the air-panel room.Thermal simulations in other cities show that the PCM panel has a better thermal performance during winter,as it helps to maintain or increase the room temperature by some degrees to reach comfort temperatures.This demonstrates that the implementation of such PCM in the building envelope can effectively reduce space heating and cooling needs,and improve indoor thermal comfort in different climates of Chile.

A Dual-driven Intelligent Combination Control of Heat Pipe Space Cooling System

Effective thermal control systems are essential for reliable operation of spacecraft.A dual-driven intelligent combination control strategy is proposed to improve the temperate control and heat flux tracking effects.Both temperature regulation and heat flux tracking errors are employed to generate the final control action;their contributions are adaptively adjusted by a fuzzy fusing policy of control actions.To evaluate the control effects,describe a four-nodal mathematical model for analyzing the dynamic characteristics of the controlled heat pipe space cooling system（HP-SCS） consisting of an aluminum-ammonia heat pipe and a variable-emittance micro-electromechanical-system（MEMS） radiator.This dynamical model calculates the mass flow-rate and condensing pressure of the heat pipe working fluid directly from the systemic nodal temperatures,therefore,it is more suitable for control engineering applications.The closed-loop transient performances of four different control schemes have been numerically investigated.The results conclude that the proposed intelligent combination control scheme not only improves the thermal control effects but also benefits the safe operation of HP-SCS.

Operational performance of a novel heat pump coupled with mini-channel PV/T and thermal panel in low solar radiation

Here we describe a heat pump system coupled with novel PV/T and thermal panels for space heating in low solar radiation conditions.Existing solar indirect-expansion systems connect the solar panels and evaporator of the heat pump in parallel with the heat storage tank.For our system these three components are instead connected in series,which can stabilize the temperature at the inlet of the evaporator and decrease the inlet temperature of the solar panels,leading to improved energy efficiency and the production of much more thermal energy.The experimental results of this system show that the average electrical,thermal and overall efficiency of the PV/T panels are 15.9%,33.4%and 49.3%,respectively.The average thermal efficiency of the thermal panels is 60.4%,the COP of heat pump is 4.7 and the room temperature is constantly over 18°C.Based on the experimental results,some improvements are analyzed.We conclude that this operating model can meet the requirement of space heating in low solar radiation environments.

Thermal Stability and Thermal Aging of Poly(vinyl chloride)/MgAl Layered Double Hydroxides Composites

MgAl-LDH（layered double hydroxides） were prepared with CO（NH2）2, NH4 Cl and NH3·H2O by the coprecipitation method, respectively. Corresponding composite membranes were prepared by the coating method. LDHs were characterized by WAXS, CO2-TPD and SEM. The morphology of the PVC/LDHs composite membranes were characterized by means of SEM. The thermal stability of the membranes was analyzed by air aging box and TGA-FTIR. The SEM results show that nano-particles can be compatible with poly（vinyl chloride）（PVC） matrix homogeneously by the stirring-ultrasound blend method with two steps. Furthermore, the air aging box results proved that MgAl-CO（NH2）2-LDH has the best effect on thermal stability of PVC. TGA-FTIR results show that MgAl-CO（NH2）2-LDH could adsorb more HCl that resulted from the degradation of PVC and improve the pyrolysis temperature of the first degradation stage by 15 K compared with PVC.

Behavior of microbubbles on spatially controlled golden nanoparticles

Incipient plasmonic bubble formation is observed around gold nanopillars with different inter-nanopillar separations. The experimental measurements and theoretical analysis show that the nanobubble formation is due to the enhanced plasmonic resonance rather than from the laser heating. Inter-nanopillar distribution may lead to threshold fluence variations. The lifetime of plasmonic bubbles can reach several minutes. Furthermore, both the radius and the growth rate of the plasmonic nanobubble increase as the inter-nanopillar distribution decreases.Smaller-spacing distributed arrays produced larger bubbles. The maximum growth rate of the bubbles can be reached at about 883.5 × 10^-6m∕s on 1 μm nanopillars, but it is only 56.9 × 10^-6m∕s on 4 μm nanopillars.