直流燃烧室内气体辐射换热特性研究

As one of the core components of aero-engine,the thermal protection scheme of combustion chamber has an important impact on its service life.In order to improve the design level of high-performance combustion chamber,the radiation heat transfer characteristics of combustion chamber are studied by experimental method.The following results are obtained:1)With the increase of oil-gas ratio,the gas temperature increases first and then tends to be stable,the radiant heat flow increases gradually,the convective heat flow increases gradually and then tends to be stable,and the proportion of radiant heat flow remains basically unchanged;2)With the increase of the inlet temperature,the gas temperature increases gradually,the radiant heat flow,especially in the flame barrel head area,increases significantly,the convective heat flow remains basically unchanged,and the proportion of radiant heat flow increases significantly;3)With the increase of the combustion chamber pressure,the gas temperature increases gradually.When the combustion chamber pressure is low,the radiant heat flow increases sharply with the increase of the pressure;When the combustion chamber pressure is high,the radiant heat flow increases slowly with the increase of the pressure.The convective heat flow gradually decreases and tends to be stable,and the proportion of radiant heat flow gradually increases and tends to be stable.This study is of great significance to improve the calculation accuracy of radiant heat flow of combustion chamber and the reliability design of thermal protection scheme of combustion chamber.

Evaluation of the thermal performance of radiant floor heating system with the influence of unevenly distributed solar radiation based on the theory of discretization

In the building with many transparent envelopes,solar radiation can irradiate on the local surface of floor and cause overheating.The local thermal comfort in the room will be dissatisfactory and the thermal performance of radiant floor will be strongly affected.However,in many current calculation models,solar radiation on the floor surface is assumed to be uniformly distributed,resulting in the inaccurate evaluation of the thermal performance of the radiant floor.In this paper,a calculation model based on the theory of discretization and the RC thermal network is proposed to calculate the dynamic thermal performance of radiant floor with the consideration of unevenly distributed solar radiation.Then,the discretization model is experimentally validated and is used to simulate a radiant floor heating system of an office room in Lhasa.It is found that with the unevenly distributed solar radiation,the maximum surface temperature near the south exterior window can reach up to 35.6℃,which exceeds the comfort temperature limit and is nearly 8.5℃higher than that in the north zone.Meanwhile,the heating capacity of the radiant floor in the irradiated zone can reach up to 171 W/m^(2),while that in the shaded zone is only 79 W/m^(2).The model with the assumption of uniformly distributed solar radiation ignores the differences between the south and north zones and fails to describe local overheating in the irradiated zones.By contrast,the discretization model can more accurately evaluate the thermal performance of radiant floor with the influence of real solar radiation.Based on this discretization model,novel design and control schemes of radiant floor heating system can be proposed to alleviate local overheating and reduce heating capacity in the irradiated zone.

Performance simulation and optimization of new radiant floor heating based on micro heat pipe array

This paper proposes two new radiant floor heating structures based on micro heat pipe array(MHPA),namely cement-tile floor and keel-wood floor.The numerical models for these different floor structures are established and verified by experiments.The temperature distribution and heat transfer process of each part are comprehensively obtained,and the structure is optimized.The results show that the cement-tile floor has the better heat transfer performance of the two.When under the same inlet water temperature and flow rate,the keel-wood floor's surface temperature distribution is about 2℃ lower than that of the cement-tile floor.The inlet water temperature of cement-tile floor is about 10℃ lower than that of keel-wood structure when the floor surface temperature is the same.During a longitudinal heat transfer above MHPA,the floor surface temperature decreases by 0.5℃ for every 10 mm filling layer increase.In order to reduce the non-uniformity of the floor's surface temperature and improve the thermal comfort of the heated room,the optimal structure for a floor is given,with the maximum surface temperature difference reduced by 3.35℃.We used research focusing on new radiant floor heating,with advantages including high efficiency heat transfer,low water supply temperature,simple waterway structure,low resistance and leakage risk,to provide theory and data to support the application of an effective radiant floor heating based on MHPA.

Physiological benefits of ambient far infrared energy within the 4-24 micron range

Far infrared(FIR)radiation(3-100µm)is an electromagnetic spectrum commonly studied for biological effects.This article aims to discuss using Far infrared radiation with sub-division(4-24µm)of this waveband to stimulate tissues and cells and is considered an effective therapeutic modality for specific medical disorders.The IR application as a medical therapy has advanced rapidly in recent years.For example,IR therapy like IR-emitting apparel and materials that can be run solely by body heat(does not need an external power supply)have been developed.New methods for providing FIR radiation to the human body have emerged due to technological advancements.Specialty saunas and lamps that emit pure FIR radiation have become effective,safe,and widely used therapeutic sources.Fibers infused with thermide,FIR emitting ceramic nanomaterials and knitted into fabrics are used as clothes and apparel to produce FIR radiation and benefit from its effects.A deeper understanding of FIR's significant innovations and biological implications could aid in improving therapeutic efficacy or developing new methods that use FIR wavelengths.