Cooling Cycle Optimization for a Vuilleumier Refrigerator

Vuilleumier refrigerators are a special type of heat-driven cooling machines. Essentially, they operate by using heat from a hot bath to pump heat from a cold bath to an environment at intermediate temperatures. In addition, some external energy in the form of electricity can be used as an auxiliary driving mechanism. Such refrigerators are, for example, advantageous in situations where waste heat is available and cooling power is needed. Here, the question of how the performance of Vuilleumier refrigerators can be improved is addressed with a particular focus on the piston motion and thus the thermodynamic cycle of the refrigerator. In order to obtain a quantitative estimate of the possible cooling power gain, a special class of piston movements (the AS motion class explained below) is used, which was already used successfully in the context of Stirling engines. We find improvements of the cooling power of more than 15%.

Stochastic thermodynamics of a finite quantum system coupled to a heat bath

We consider a situation where an N-level system (NLS) is coupled to a heat bath without being necessarily thermalized. For this situation, we derive general Jarzynski-type equations and conclude that heat and entropy is flowing from the hot bath to the cold NLS and, vice versa, from the hot NLS to the cold bath. The Clausius relation between increase of entropy and transfer of heat divided by a suitable temperature assumes the form of two inequalities which have already been considered in the literature. Our approach is illustrated by an analytical example.

EFFECTS OF DIFFERENT FLAME RETARDANT TREATMENTS ON THE COMBUSTIBILITY OF BAMBOO FILAMENT

Bamboo filaments were treated with boric acid and borax (the mass ratio of 1:1, the concentration of 20%) with four different treatment methods including atmospheric immersion, cold and hot bath immersion, vacuum impregnation and vacuum-pressure impregnation. The different treatment methods on the boron loading were analyzed and the corresponding flame resistance of bamboo filaments were evaluated by the cone analysis. The results showed that suitable treatment method with optimized processing indexes, such as hot and cold bath immersion in the condition of 100°C/2 h and 20°C/2 h with 3 cycles, was more credible to accelerate the percentages of boron loading in the bamboo filaments, and the lowest result was found in the samples with vacuum impregnation. Compared to the untreated samples, the heat and smoke release would be decreased significantly, especially for the samples with the promising hot and cold treatment, and promising pressure treatment, attributed to the more stable boron fixed in the bamboo filaments.

PREPARATION THE ROSE-LIKE HYDROPHOBIC SURFACE OF WOOD BASED MATERIALS BY SOFT LITHOGRAPHY

Bamboo filaments were treated with boric acid and borax (the mass ratio of 1:1, the concentration of 20%) with four different treatment methods including atmospheric immersion, cold and hot bath immersion, vacuum impregnation and vacuum-pressure impregnation. The different treatment methods on the boron loading were analyzed and the corresponding flame resistance of bamboo filaments were evaluated by the cone analysis. The results showed that suitable treatment method with optimized processing indexes, such as hot and cold bath immersion in the condition of 100°C/2 h and 20°C/2 h with 3 cycles, was more credible to accelerate the percentages of boron loading in the bamboo filaments, and the lowest result was found in the samples with vacuum impregnation. Compared to the untreated samples, the heat and smoke release would be decreased significantly, especially for the samples with the promising hot and cold treatment, and promising pressure treatment, attributed to the more stable boron fixed in the bamboo filaments.

A U-Shaped Oscillatory Liquid Piston Compression Air Conditioner Driven by Rotary Displacer Stirling Engine

A rotary displacer, Stirling engine-driven, oscillatory liquid piston-compression air conditioning unit is analyzed, designed, and conceptually proved by experiments on its cooling capability and performance efficiency. The engine itself aims to work compatibly with a conventional solar water heater as its power source, with a rotary displacer to manipulate its operation frequency. A U-shaped, oscillatory liquid piston, with the cylinder chamber vented to low pressure, aims to both reduce the sealing friction and serve as the refrigerant. During the experiments, the engine is fed with an electrically heated hot bath whose temperature profile is determined according to a field test of solar thermal collectors in summer conditions. Experimental results show that the coefficient of performance (COP) of the oscillatory liquid piston air conditioning unit would be in the range of 1.3 to 1.5.

Multidisciplinary Approach to Characterize Archaeological Materials and Status of Conservation of the Roman Thermae of Reggio Calabria Site (Calabria, South Italy)

This multidisciplinary research focuses on diagnostic investigations to characterize the archaeological materials, as well as the alteration and degradation forms detected at the Roman Thermae of Reggio Calabria (Calabria, South Italy) site. The thermal complex, (dating I–II century B.C.), was built around three main rooms such as the caldarium (hot bath), the tepidarium (warm bath) and the frigidarium (cold bath), all connected to a central room through several entrances. The central hall still preserves a suggestive mosaic floor dating between the II and III century A.D., characterized by geometric motifs and black and white tesserae. Fragments of various archaeological stone materials, such as bricks, mortars, sedimentary, volcanic and metamorphic rocks have been studied with different and complementary techniques. Particularly, polarized optical microscopy (POM) and X-ray diffractometry (XRD) were performed to characterize the materials employed to construct the site and evaluate their state of preservation. Finally, laboratory microbiological culture analysis was conducted to identify the main microorganisms composing the biological patinas detected on the sampled materials. Results allowed us to evaluate the most suitable restoration procedures to conduct at the archaeological site, considering the different stone materials present in the studied area and their state of conservation.

Constructing Machine Tool Foundations Using an LMP Alloy

Currently, the construction of machine tool foundations is a complicated and lengthy procedure with a limited flexibility. In this paper, we present a novel system for constructing machine tool foundations that replaces the need for concrete or concrete-polymer hybrids with a low melting point (LMP) alloy. The system uses a hot bath method to maintain the LMP alloy grouting in liquid form. A fixing device is used to control the embedded depth and positional accuracy of the foundation bolt assembly. The grouting material is injected into the foundation pit by a filling device. This can be extracted from the foundation pit in a later stage with the aid of a recycling device, enabling new machine tool foundations to be manufactured by reusing the LMP alloy grouting material. A prototype was built to test the proposed design. The results show that the system can construct machine tool foundations in a single application, without the delays associated with concrete-based construction, lowering both the economic and environmental cost.

HOT BATH THERAPY FOR POSTPARTUM MOTHERS: THE ETHNOCARING PRACTICE IN THE MUNA TRIBE, SOUTHEAST SULAWESI, INDONESIA

Background: Postpartum mothers are vulnerable to postpartum fatigue, delivery process fatigue, and role transition. The unknown fatigue can trigger stress and anxiety that will lead to postpartum blues and postpartum depression. The ethnocaring of the Muna tribe has a series of care that can prevent postpartum fatigue, including a hot bath. Objective: To explore the ethnocaring practice on the postpartum care method in the Muna tribe using hot bath and analyze it scientifically. Methods: This study was a qualitative study with an ethnographic approach. The participants were 15 Muna’s indigenous midwives and 4 Muna’s mothers. Snowball sampling was employed to select the samples. The data were collected through in-depth interviews, focus group discussion and participatory observation. The data validity was made by completing the trustworthiness criteria process.Results: The results of the study were described into 3 themes, namely equipment, treatment, and prohibition. The equipment theme describes tools and materials. Conclusion: The ethnocaring therapy of a hot bath in Muna’s postpartum mothers has healthy benefits namely for relaxation, increasing the oxygen uptake, increasing concentration and revitalizing the reproductive organs.

Performance of resident nurses in obstetrics on childbirth care

Objectives: to describe good practices on childbirth care and obstetric interventions performed by resident nurses in obstetrics during the obstetric childbirth risk at a public maternity hospital in Salvador. Methods: a descriptive cross-sectional study with a quantitative approach, based on the of 102 parturients, between February and April 2016. The data collection was performed through the collection of information on clinical files for analysis by using descriptive statistics with absolute and relative frequencies for the evaluated categorical variables. Results: it was observed that 100.0% of the women used some kind of non-pharmacological method for pain relief, although the method of choice was to take a hot bath; 99.0% of the women drank liquids; 94.0% had the presence of a companion of free choice; 99.0% walked during labor; 100.0% had the freedom to choose a position during childbirth. It is noteworthy that no woman in this study was submitted to episiotomy, and more than 70.0% were not submitted to any obstetric intervention. Conclusions: the Programa de Residência em Enfermagem (Residency Nursing Program) an important point in the childbirth humanization process is directly associated to the increase in the normal childbirth rates, the highest use on good practices in childbirth care, and the reduction on obstetric interventions.

Self-propulsion of inverse Leidenfrost drops on a cryogenic bath

When deposited on a hot bath, volatile drops are observed to stay in levitation: the so-called Leidenfrost effect. Here, we discuss drop dynamics in an inverse Leidenfrost situation where room-temperature drops are deposited on a liquid-nitrogen pool and levitate on a vapor film generated by evaporation of the bath. In the seconds following deposition, we observe that the droplets start to glide on the bath along a straight path, only disrupted by elastic bouncing close to the edges of the container. Initially at rest, these self-propelled drops accelerate within a few seconds and reach velocities on the order of a few centimeters per second before slowing down on a longer time scale. They remain self-propelled as long as they are sitting on the bath, even after freezing and cooling down to liquid-nitrogen temperature. We experimentally investigate the parameters that affect liquid motion and propose a model, based on the experimentally and numerically observed (stable) symmetry breaking within the vapor film that supports the drop. When the film thickness and the cooling dynamics of the drops are also modeled, the variations of the drop velocities can be accurately reproduced.