Compression-type heat pumps have been employed in many fields of refrigeration and air conditioning for achieving energy savings. In addition, the system operates at high efficiency under a variety of operating conditions throughout the year through various innovative components, such as the inverter, and the annual performance improvement. However, the running time of the system over the year under low load conditions is very long, and under such conditions, the system operates intermittently because of the difficulty in the continuous running of the compressor. Of course, because intermittent driving is made under such an operating condition, the performance can estimate that it decreases greatly easily, but it is the present conditions that field operation performance does not become clear almost. Therefore, the key goals of this study were to clarify the intermittent driving performance of the compression-type heat pump and to devise a way to improve its performance and develop an optimum operation method. As the first step, we constructed a mathematical model that can predict intermittent driving characteristics at the time of low load of the pump, which are crucial to investigation of the performance. The constructed model was validated experimentally. In summary, a mathematical model of the compression-type heat pump was constructed, and its validity was demonstrated via comparison of its results with those obtained experimentally.
In this study, speeds of sound in HFO-1234yf near saturated and subcooled liquid phases were measured with a sound velocity sensor. The measurement for near saturated liquid was conducted at the temperature range of 273 to 353 K, and that for subcooled liquid was conducted at ranges of temperature from 273 to 353 K and pressure from 1.05 to 2.52MPa. In order to validate the sound velocity sensor, the measurements in subcooled water and near saturated liquid of HFC-134a at the temperature range from 273 to 353 K were also performed. The measurement result of water was compared with those calculated from REFPROP (based on IAPWS-95) and PROPATH (based on IAPWS-IF97). The result of water agrees well with that calculated from REFPROP with a maximum deviation of 0.28%, except for the temperature of 353 K. And it agrees well also with that calculated PROPATH with a maximum deviation of ±0.2%. The measurement results for near saturated and subcooled liquid of HFO-1234yf were compared with those calculated from REFPROP and JSRAE thermodynamic table.
The cryoprotectant is commonly used to protect reproductive tissues during freezing and thawing. As an effort to investigate the osmotic behavior of cryoprotectant, near-infrared (NIR) techniques were applied to monitor the concentration of ethylene glycol (EG) within reproductive tissues. Spectroscopic analysis showed an absorption peak at 1460 nm for pure water, and the peak wavelength was increased by increasing EG concentration. Pure EG showed an absorption peak at 1586 nm. Based on this observation, a bandpass filter with a center wavelength of 1450 nm was selected to monitor EG concentration from NIR images by estimating water contents. The NIR image of pure EG showed an absorbance value as low as 2.419 due to high intensity at 1450 nm while that of pure water reached 2.902. A linear relationship was assumed between the absorbance value of image and EG concentration and was applied to the NIR images of mouse ovarian tissues soaked in 50% EG solution by weight. This procedure allowed the visualization of the concentration distribution of EG within reproductive tissues and also the analysis of osmotic behavior of EG according to time after soaking.
Since the occurrence of the Tohoku Region Pacific Coast Earthquake on March 11 in 2011, peak load reduction of the daytime electric power has been more important in Japan. One of the efficient measures against the daytime peak load reduction in hot season is to use appropriate thermal storage system at the nighttime. Tetra-n-Butyl Ammonium Bromide (TBAB) organic hydrate slurry is being used to facilitate the development- and application-related advancements in thermal storage and air-conditioning systems. The fundamental thermophysical properties of the TBAB aqueous solutions; refractive index, density and viscosity, as well as the empirical equations of these properties, are presented in this paper.
We invented and studied a new ice making system, in which a cooling plate freezes water through a thin metallic belt and protected ice is removed from on the plate by moving the belt. It is shown that the system is able to make long and plate-like ice continuously for more than four hours. The thickness of the ice can range from 1 to 8 mm depending on belt feed speed and temperature of the cooling plate. Then, from a measured mass rate of ice production, we calculated thermal contact resistance between the cooling plate and the belt, which is an important parameter for evaluating ice-making performance of the system. In the results, it is found that the resistance, which is significantly decreased by increase of the belt feed speed, can be low enough not to hinder the ice-making performance. Additionally, feeding the belt back and forth with short strokes is to be effective in reducing the resistance while maintaining the thickness of the plate-like ice.
Experiments were carried out to observe the vapor-liquid two-phase flow of a refrigerant R 410A in small diameter glass tubes. The cross-sectional shapes of the glass tubes were circular, rectangular, and triangular, and their hydraulic diameters were 1.03, 0.97, and 0.82 mm, respectively. Flow directions were vertical upward, downward, and horizontal. Two-phase flow patterns were observed with a high-speed camera for mass velocity ranges from 30 to 400 kg/(m2·s) and qualities between 0.05 and 0.9 at the saturation temperature of 10 ℃ under adiabatic condition. The vapor and liquid superficial velocities were taken as 0.036 - 8.588 m/s, and 0.003 - 0.337 m/s, respectively. Based on the present observations, flow patterns were classified into several flow regimes, and the effects of the cross-sectional shape and flow direction on the flow pattern were clarified. Furthermore, conventional flow pattern maps for mini-channels were compared with the present observation results, and new flow pattern maps were proposed. In addition, the evaporation heat transfer through thin liquid film was confirmed through the observation with heating.
It is important to evaluate the annual performance factor (APF) of room air conditioners (RACs) in accordance with their actual usage in residential sectors. In this study, actual RAC usage was monitored for 100 families over a year by equipping each air conditioner with an electric power meter and a data logger. We monitored 25 families living in detached houses in the Shinetsu area (a cold area), 25 families in the west Kanto area, 25 families in the east Kanto area, and 25 families living in apartments in the east Kanto area. After analyzing the obtained data, two types of operating ratios were introduced—an outdoor-temperature-associated operating ratio (TOR) and an hour-associated operating ratio (HOR). It was found that there is essentially little difference in the TOR and the HOR among the monitored sections or the monitored months in the same season from the standpoint of the sectional or monthly average. We also performed a simple questionnaire survey and compared to the measured data.
It is important to evaluate the annual performance factor (APF) of room air conditioners (RACs) in accordance with their actual usage in residential sectors. In this study, actual RAC usage was monitored for 100 families over a year by equipping each air conditioner with an electric power meter and a data logger. We monitored 25 families living in detached houses in the Shinetsu area (a cold area), 25 families in the west Kanto area, 25 families in the east Kanto area, and 25 families living in apartments in the east Kanto area. In this report, we showed the results of a cluster analysis on an outdoor-temperature-associated operating ratio (TOR) and an hour-associated operating ratio (HOR), and the most influential operation pattern for the total operating time was ascertained. Finally, an appropriate and simple method for obtaining the APF of actual RAC usage is outlined.