Thermal performance of new flat plate solar air heater based on micro-heat pipe arrays (MHPA)

Tingting Zhu, Yanhua Diao*, Yaohua Zhao, Cheng Ma, Fengfei Li

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

10 Citations (Scopus)


In common types of flat-plate solar air heaters, the uneven flow and heat exchange between air and an absorber plate poses a problem. To resolve this problem, this paper proposed a novel type of flat-plate solar air heater based on micro-heat pipe arrays (MHPA). An investigation was carried out on the design, thermal performance and flow resistance characteristic of the novel heater based on micro-heat pipe arrays. The new air collector consists of 15 MHPAs with V-shaped fins attached to the heat release (condenser) section, absorber film, insulation board, bottom plate, and air ventilation and heat exchange section. The components of the heater include the toughened glass cover, air layer (35 mm), MHPA-absorber plate, thermal insulation layer, and the back board. Solar energy is absorbed by the MHPA evaporator section with the organic combination of high efficiency absorber film, which formed a heat pipe effect within each micro heat pipe arrays. The heat has been released to the air in the ventilation and heat exchange section of the heater, whereas the air was eventually warmed. Simultaneously, the working medium in MHPA proceeds continuous phase transition cycle and continuously passes solar radiation heat to air in the air duct with high efficiency. The MHPA heat-absorbing plate core can realize the whole area of heat absorption, high efficient heat transmission, and large surface of heat release. The total solar energy is received by the heater, and some energy is transferred to the air flow in the air duct as useful energy; the remaining energy is lost mainly through the glass cover, frames, bottom plate, and air duct. The heat loss through the frames and the air duct can be ignored because of good heat preservation condition. So the glass cover becomes the main source of heat loss. Thermal analysis shows that heat loss through the glass cover occupies the largest proportion of the total heat loss of the heater.To test the new heater thermal efficiency and the influence of various factors on the performance of the MHPA flat-plate SAC, an experimental system was constructed for thermal performance in Beijing. The system can be divided into two sub-systems: the new heater testing system and meteorological parameter testing systems. During the testing period, the air temperature of inlet and outlet of the heater, different temperature points, air flow rate, ambient temperature, and the solar irradiation were measured under different conditions. The inlet and outlet air temperatures were measured with four thermal resistors installed on the cross section of the air duct, respectively. The experiment data was recorded by an Agilent 34970A data acquisition system. Meteorological parameters (including the solar irradiation intensity, ambient temperature, humidity, wind speed and direction) were provided by the weather stations. The measurement of air volume flow rates were completed by the air volume cover. Four different operating conditions were carried out with different air volume flow rates. The effects of weather condition and operating parameters on the thermal performance of the heater were also studied. Heat transfer enhancement can be achieved with a high volume flow rate which due to the convective heat transfer between air and the fins can be enhanced. When the air volume flow rate decreased, the efficiency obviously decreased. The experimental results showed that the efficiency of the heater was approximately 68% with the flow rate of 290 m3/h. The pressure drop was less than 10.4 Pa when the flow rate was less than 290 m3/h. And the frictional coefficient had also been determined. The new heater shows excellent performances with simple structure, high reliability, and stable thermal efficiency.

Original languageEnglish
Pages (from-to)250-257
Number of pages8
JournalNongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering
Issue number11
Publication statusPublished - 1 Jun 2016
Externally publishedYes


  • Frictional factor
  • Heat transfer
  • Micro-heat pipe arrays
  • Solar air heater
  • Solar energy
  • Thermal efficiency
  • n/a OA procedure


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