Psychrometric Charts Research Articles

A novel phase-field lattice Boltzmann framework for diffusion-driven multiphase evaporation

Heat transfer and phase change phenomena, particularly diffusion-driven droplet evaporation, play pivotal roles in various industrial applications and natural processes. Despite advancements in computational fluid dynamics, modeling multiphase flows with large density ratios remains challenging. In this study, we developed a robust and stable conservative Allen–Cahn-based phase-field lattice Boltzmann method to solve the flow field equations. This method is coupled with the finite difference discretization of vapor species transport equation and the energy equation. The coupling between the vapor concentration and temperature field at the interface is modeled by the well-known Clausius–Clapeyron correlation. Our approach is capable of simulations under real physical conditions and is compatible with graphics processing unit architecture, making it ideal for large-scale industrial simulations. Three validation test cases are conducted to demonstrate the consistency of the presented model, including simulations of Stefan flow, the evaporation of suspended droplets containing water, acetone, and ethanol in the air, and the evaporation of a water sessile droplet on a flat surface. The results show that the model is able to predict the behavior and characteristics of each case accurately. Notably, our numerical results exhibit a maximum relative error of approximately 1% in simulations of Stefan flow. In the case of suspended droplet evaporation, the observed maximum difference between the calculated wet bulb temperatures and those derived from psychrometric charts is approximately 0.9 K. Moreover, our analysis of the sessile droplet reveals a good agreement between the results obtained by our model for the evaporative mass flux and those obtained from the existing models in the literature for different contact angles.

Monitoring Environmental Factors Associated with Indoor Growth Chambers and Greenhouses for Cannabis Cultivation

Greenhouse cultivation has no seasonal limitations and research is being conducted globally to assess control of environmental factors within greenhouses to optimize growing conditions. Attempts to improve the environmental factors in greenhouse cultivation include control of temperature, relative humidity, light intensity, carbon dioxide level, and air flow rate. Furthermore, indoor cultivation systems (growth chambers) have been developed and researched for comparison with greenhouse cultivation. In our study, comparative environmental data were collected in association with cannabis cultivation for a greenhouse and growth chamber, since commercial cannabis cultivation can include such methods. Accordingly, the data in this research were collected by choosing the same cannabis cultivars for both cultivation methods and by controlling the internal growing environments that affected cultivation. Data also were collected on the plant biochemical properties over the same time period and the collected data were analyzed using psychrometric charts. The findings of this research show that if the internal environment of the indoor cultivation method is well-regulated, better results in cannabidiol (CBD) extraction from blossoms can be achieved as compared to greenhouse cultivation, in which environmental regulation is less precise. Therefore, we conclude that if we can control the internal environment of greenhouse cultivation to be similar to the indoor cultivation method, the productivity of the two methods should be similar. The findings of this research can be used to develop greenhouse cultivation methods for other plants in order to improve future productivity and efficiency.

Multi-objective optimization of desiccant wheel via analytical model and genetic algorithm

The dehumidification performance and energy consumption of desiccant wheel are affected by many design parameters and operating variables. However, there are few researches concerning multi-objective optimization. Therefore, an optimal design framework combining analytical model, multi-objective optimization and decision-making is proposed. The model was based on the overall heat and mass balances, so the objective functions of the desiccant wheel were derived, and the constraints for the equilibrium of the adsorption and desorption were obtained. Then, the non-dominated sorting genetic algorithm II (NSGA-II) was employed to calculate the Pareto optimal front of the two-objective optimization, and the results were analyzed with psychrometric chart. This solution set includes not only the optimum one with the design method of psychrometric charts, but also includes other better solutions. From the Pareto solutions, the final optimal solution was obtained with the technique for order preference by similarity to ideal solution (TOPSIS) based on four criteria. With the final optimal parameters applied to existing example, the further improvements on the outlet process air humidity ratio and the dehumidification coefficient of performance were found.

Approximate climate analysis for assessing the suitability of Indian climate zones for hydroponic fodder applications

Hydroponic fodder has been proposed as a novel low-tech solution to India’s fodder scarcity. Hydroponic fodder can reduce water requirements by up to 95% and use up to 70% less land due to their vertically scalable nature. The short crop cycles of approximately 7 days yields a seed to feed ratio of 1:8. This study analyses the external environmental weather conditions in Indian climate zones, assessing their suitability for the application of hydroponic fodder solutions. The weather of each climate zone was approximated by a representative city through parameter selection and optimisation by three-dimensional Euclidean distance minimisation. Simulation and analysis were carried out on the Rhinoceros software platform with the Grasshopper and LadyBug plug-ins. Hourly temperature plots, sun-path diagrams and psychrometric charts with modified predicted mean vote polygons superimposed were generated for each climate zone. The ambient weather suitability of the following representative cities was simulated to be as follows: Ahmedabad (86.70%), Kolkata (81.86%), Bengaluru (94.07%), Lucknow (73.23%) and Srinagar (30.85%). A cost benefit analysis was buttressed by a sensitivity analysis with respect to the selling price of green fodder. A preliminary cash flow analysis yielded a discounted payback period of 4 months for direct fodder sales and 20 months for sale of livestock products as a co-benefit of green fodder production.

Computational psychrometric analysis as a control problem: case of cooling and dehumidification systems

Psychrometric chart is a basic tool for analysis of processes in air-conditioning systems. While psychrometric calculators and numerical psychrometric charts are widely available, there is a lack of numerical algorithms for solving the sizing problem by using psychrometric analysis. After introducing a classification of modelling problems in direct and inverse (based on the relation between physical and computational causality), this paper defines the design problem as a set of inverse problems of control and parameter optimization. A non-linear model is obtained by assembling the models of the elementary processes. The paper proposes to solve the direct and control problems by using a method similar to Newton-Raphson’s, and the parameter optimization problem by using least-squares. Open-source implementation, published on Zenodo repository, and interactive, reproducible environment, available on Binder web service, accompany this paper (Ghiaus [2021]. PsychroAn_cool: Psychrometric analysis of cooling systems as a control problem. Zenodo.).

Investigation of energy savings potential of multi-variable differential temperature control in economizer

• This study proposed multi-variable temperature-based controls for economizers. • The proposed controls additionally considered latent loads in the typical temperature-based methods. • The results showed the substantial savings potential of system cooling loads in the proposed controls. In commercial buildings, building mechanical systems use over 33–50% of the total building energy consumption. As an energy conservation measure, an economizer can be used to reduce energy consumption and operating costs by introducing cold outdoor air into building space based on the outside air temperature or enthalpy. Among control types of economizer, enthalpy-based control is the more energy-efficient approach for the economizer cycle in Korea. However, in reality, humidity sensors are often out of order in buildings, which disables enthalpy-based controls in economizers. Therefore, as a practical substitute, multi-variable temperature-based control was investigated in this study using the local outdoor air humidity to consider latent loads in the typical temperature-based control and supplement the frequent failures of humidity sensors. The results showed the substantial energy savings potential in temperature-based control, which is driven by reduced system loads in cooling coils in a mixed-humid climate. Also, an analysis of the psychrometric charts represented that the impact of multi-variable temperature-based control would be more significant in humid climates than dry or marine regions. The proposed approach can complement the conventional differential dry-bulb temperature control method and provide a guide for improved economizer operations to achieve better energy performance in hot and humid climates.

Review on low‐temperature heat pump drying applications in food industry: Cooling with dehumidification drying method

AbstractMoisture content of food material is a key factor influencing the quality of storage and extending the quality of a food product. Manufacturers develop new technologies to process sensitive food materials to supply new products with improved properties and high quality. The process in which the air is cooled sensibly while the moisture is removed from food is called cooling with dehumidification process. The system fundamentally acts as a heat pump, which pumps the heat from the dehumidified air to a different air stream in another area, with the aid of a refrigerant gas to carry the heat. This article reviews the potential of low‐temperature heat pump dehumidifier drying used in the food industry. Moreover, this describes the principle of cooling with dehumidification (CWD) process, the importance of studying psychrometric charts to understand CWD process, measures used in identify energy efficiency, comparison of this method over common dryers, applications, advantages and limitations of the CWD drying method.Practical applicationsMultiple measures have been taken to increase the drying efficiency of convection drying, especially by the application of cooling with dehumidified techniques. This drying technique has comparably higher energy efficiency, better and consistent product quality and the ability to control drying temperature and humidity over other conventional methods. Low‐temperature heat pump dryers are used increasingly applications in the food industry for the drying of grains, fruits, vegetables, herbs, spices, fish, meat, pet foods, and other heat‐sensitive food products in several countries.

Web-based real time air properties display application

A point on the psychrometric chart can show 7 properties of air. If two properties are known then 5 other properties can be calculated. Air treatment will change the properties of air conditions. Changes in air condition can be determined by measuring each air properties and plotted on a psychrometric chart. One of the uses of psychrometric analysis is to determine the amount of cooling capacity used in air conditioning systems. To show the condition of the air at any time needed a system that is integrated between the data acquisition device and data display. This research designs and develops applications that are ready to display data and psychrometric charts that can later be integrated with hardware equipped with sensors through an interface. Psychrometric applications are designed using the JavaScript programming language, so they can be opened using any web browser. Psychrometric charts are drawn using iteration calculation methods. Based on the results of data analysis, the difference in value between the results of manual calculations and applications is as follows: wet-bulb temperature (Twb) is 0.27%, Moisture Content (ω) is 0.77%, specific enthalpy (h) is 0.52 %, Specific Volume (v) is 0.28%, Dew-Point Temperature (Tdp) is 0.92%.

Towards synthetic fuels production from biomass gasification: Tar content at low temperatures

Biomass conversion into biofuels and biogas is a promising way for power and heat generation. Lately, research has focused on the production of biomethane based on biomass gasification followed by methanation as an alternative to fossil natural gas. The challenge of this process remains in the intensive gas cleaning and required tar removal. In order to study tar removal from the producer gas downstream biomass gasification, solid–vapor and liquid–vapor equilibrium must be known for different tar concentrations, ranging between 0.001 and 100 g.Nm−3. To assess tar removal by condensation at low temperatures, psychrometric charts are developed. Since the composition of tar is complex, toluene, phenol, indene, naphthalene and fluoranthene are selected as tar representatives. Each component is studied separately in four different producer gas compositions formed mainly of hydrogen, carbon monoxide, carbon dioxide and methane in addition to water and nitrogen. Methods for calculating saturation, isenthalpic and constant relative concentration lines are presented. Psychrometric charts of the different tar components are finally plotted at atmospheric pressure. Results show that temperature of 196.15 K is required to reduce the tar content to 0.001 g.Nm−3.

AUTOMATIC SYSTEM FOR PSYCHROMETRIC CALCULATIONS

Air psychrometric properties are important in several areas of agricultural engineering, such as calculation of evaluation of the animal environment and air control in grain storage units. Due to their relevance and the complexity and the uncertainties in the use of psychrometric charts, the objective of this paper was to develop the software, PsyCalculator, which stands out for the automated function that allows presenting the data acquired through sensors and the respective psychrometric properties of the air, either in graph or tables. The automatic data acquisition system consists of a microcontroller that performs readings of sensors that measure the dry bulb temperature and another variable, which may be: wet bulb temperature, relative air humidity or dew point temperature. Then, the values are sent to the PsyCalculator software system. In addition to the values ​​of dry bulb temperature, the software system presents wet bulb temperature and dew point temperature, values ​​of saturation vapor pressure, vapor pressure, mixing ratio, specific volume, enthalpy and degree of saturation. Among the psychometric variables analyzed, the software developed in the study presented a maximum error of 2.14% for the calculation of dew point temperature. The developed software allows the automation of systems that depend on the psychrometric parameters in a friendly and precise fashion.

SUSTAINABLE ARCHITECTURAL DESIGN AS AN INPUT TO RESPOND THE SOCIAL AND PSYCHOLOGICAL NEEDS FOR USER. STUDY CASE: AHMADI AREA, KUWAIT

In the context of preserving the environment as well as natural resources against corruption and continuity of life in Kuwait, this study was initiated with the objective of identifying sustainable architectural design to meet the social and psychological needs of the user, where Ahmadi area was selected a case study in Kuwait. Previous studies in the field of sustainable architectural design and social and psychological needs were reviewed. The metrological variables so as the psychrometric charts of Ahmadi were deduced and applied to a building in the study area using Ecotect Architectural Program with real data. Also, architectural and social psychological questionnaire were designed and distributed among a number of residents of the building so as qualified individuals. The results of the metrological, psychrometric so as the questionnaire results were analyzed and discussed in order to select the most effective design method. Finally, conclusions were deduced to implement the most efficient procedure in practice (ventilation so as direct and indirect evaporative cooling). In addition, some recommendations were suggested for the engineering practice and future studies

Psychrometric charts in color: An example of active learning for chemical engineering students and faculty members

This paper reports the design and scale-up of an active learning exercise centered around color coding of psychrometric charts. The initial version of this exercise was used with small classes of 60 students. When the class size doubled to 120 students, the previously successful exercise failed. The failure was then used as a workshop example for faculty development. Workshop participants successfully identified a number of details of planning and implementation which could be improved, and the revised exercise was once again successful in the classroom. The results are a framework for design of active learning exercises, a number of lessons learned about how to successfully implement active learning in large classes, and a highly polished 2-lecture unit on psychrometric charts, including two animated and worked examples which form part of the paper.

Analysis on the Utilization of Temperature and Humidity Independent Control Air-conditioning System with Different Fresh-air Handling Methods

The presented research illustrates the characteristics of Temperature and Humidity Independent Control (THIC) system with different fresh-air handling methods through engineering case studies. The investigated methods include dehumidification with the application of cooling, liquid desiccant, dual cooling sources dehumidification and dehumidification wheel. By analyzing the dehumidification processes on psychrometric charts, this study summarized main design focus then conducted detailed calculation for equipment sizing. Furthermore, this study compares energy consumptions for the four methods. Results show liquid desiccant and dual cooling sources dehumidification are more suitable for general office buildings in terms of energy conservation. Dehumidification wheel method consumes too much energy therefore not applicable for comfort air conditioning systems.

A mathematical model of commodity wet-bulb temperature (CWBT) for grain storage applications

Commodity wet-bulb temperature (CWBT), which is the value of wet-bulb temperature of the interstitial air within a grain bulk, is an important insect control term in grain storage applications. However, due to difficulties in its measurement and also the need for iterative calculations, its application for aeration control has been limited in commercial grain industries throughout the world. In the present study, a remedy to these difficulties is introduced. A straightforward model was developed by applying dimensional analysis methods to the CWBT data obtained from iterative solutions of the original wet-bulb temperature equation. This model is capable of determining non-iteratively CWBT as a function of dry-bulb temperature and relative humidity inside the grain bulk. The values of coefficient of determination (R2), mean bias error (MBE), standard error (SE) and root mean square error (RMSE) for obtained CWBT model were 0.999, 4.71%, 0.015 °C and 0.319 °C, respectively, when compared with original data, which reflect accurate predictions. The model predictions were compared with available data from valid psychrometric charts. The mean relative deviation (MRD) was less than 1.85%. The model was further applied to determine the errors in calculation of CWBT as affected by uncertainties in dry-bulb temperature and relative humidity measurements. This enhanced the capability of the model to be applied in CWBT aeration controllers.

On regression for samples with alternating predictors and its application to psychrometric charts

We introduce and study a new type of regression that arises from a kinesiology experiment concerning human's tolerance to temperature and water vapor pressure. In the experiment, a set of pressure and temperature values are collected to construct a psychrometric chart. The problem differs from traditional regression because, for one part of the data, temperature is held fixed while pressure is raised to an equilibrium point; for the other part of the data, pressure is held fixed while temperature is raised to an equilibrium point. The purpose of this peculiar design is to ensure the safety of the participants. Traditional regression is inadequate for modeling this type of data, because the roles of predictor and response alternate. We propose a new regression where the predictor and response alternate while being linked by a bijective function. We study the population and asymptotic properties of this regression, develop test statistics for model selection and analysis of variance, and outline several extensions and refinements. We apply the method to kinesiology data and find, among other things, that the gender difference in psychrometric charts diminishes in old age.

Thermal Comfort in a Refurbished Low-Energy House: The OEKOHAUS Case Study

This contribution presents the results of a long-term thermal comfort monitoring effort in the so-called OEKOHAUS building in Petronell, Lower Austria. This building mainly acts as an educational facility for the Museum of Natural History of Vienna and includes also office and short-term occupancy spaces. It was established in an existing building, adapted and refurbished in 1996. At the time of refurbishment, it clearly exceeded the applicable standard thermal requirements for building elements. Given the building's unique mixed use, it displays a highly fluctuating occupancy pattern. Subsequent to the recent installment of energy and indoor climate monitoring system, multiple streams of data are being collected. Specifically, indoor environmental variables relevant to thermal comfort in a number of zones in the building have been monitored and evaluated. Collected data include indoor temperature and relative humidity, which were represented and analyzed for different zones of the building in terms of psychrometric charts (for a monitoring period in Winter 2012/13). Moreover, indoor CO2 concentration was monitored to address indoor air quality conditions. The paper presents the monitoring results and their meaning within the larger context of a monitoring-based holistic building performance assessment strategy.

Web application for thermal comfort visualization and calculation according to ASHRAE Standard 55

Thermal comfort is one of the fundamental aspects of indoor environmental quality and it is strongly related to occupant satisfaction and energy use in buildings. This paper describes a new web application for thermal comfort visualization and calculation according to ASHRAE Standard 55-2013. Compared to existing software, the web application is free, cross-platform, and provides a visual and highly interactive accurate representation of the comfort zone. Its main features are: dynamic visualization of the comfort zone on psychrometric, temperature-relative humidity, and adaptive charts; new implementation of the Elevated Air Speed model; local thermal discomfort assessment; compliance document automation for LEED thermal comfort credits; metabolic activity and clothing insulation tables and dynamic models; and compliance with the standard. The tool can be used by architects, engineers, building operators, educators, and students.

Selection and Assessment of Passive Cooling Techniques for Residential Buildings in Oman Using a Bioclimatic Approach

Passive cooling is an ancient technique used in air reconditioning and ventilation. Despite its historical use, its relevance in building design has never ceased. To be sure, with the increasing interest in saving energy and preserving the environment, passive cooling stands out as a sustainable possibility. However, this is not always a viable option, and its practicality is determined mainly by the system's functionality, the type of activities involved in the space to be cooled, and the surrounding area's bioclimatic variables (i.e. temperature, humidity, and diurnal temperature differences). In areas under consideration for passive cooling systems, bioclimatic charts are helpful. Comprehensive charts, in which yearlong hourly meteorological data are projected on a psychrometric chart, help to determine the fits required by a particular location. In this paper, psychrometric charts were developed for eight locations in Oman, and a systematic procedure on the selection and viability of using passive cooling techniques is provided through meteorological data. Givoni's passive cooling zones are used and the applicability of each technique is quantified. The eight study locations are widely scattered around and Oman, and possess great geographical diversity. The presented results can help delineate the applicability of each passive cooling technique for residential buildings at each of the study locations and their proximities.

The impact of thermal comfort in the perceived level of service and energy costs of three Brazilian airports

To evaluate airports' current thermal comfort temperature and humidity were registered in three main Brazilian international airports, other variables were local region climate characteristics and the constructive types of passenger terminal buildings. The Brazilian air transportation demand has considerably grown over the last decade, with some airports reaching their capacity. Thermal discomfort may be a key driver of passenger perceptions of airport service levels, specially under capacity overload situations. Therefore, to achieve airport thermal comfort within this new scenario, and with the imminent and future expansions of the airport system, certainly put extra work on the existing air conditioning systems, consequently increasing energy consumption and its associated costs. Collected temperature and humidity from each study case subsided the data for the psychrometric charts. The evidences showed temperatures below the international standards requirements for thermal comfort levels. These charts also indicated that adequate building types with natural air circulation, provides the best levels of thermal comfort. Results suggest the importance of considering the implementation of a combined system using artificial and natural air conditioning in the planning of future expansions.

CALCULATIONS OF THE OUTLET AIR CONDITIONS IN THE DIRECT EVAPORATIVE COOLER

An equation capable to accurately calculate the wet bulb temperature from the ambient temperature and relative humidity is presented in this paper. Equations for calculation of the outlet air temperature and relative humidity in the direct evaporative cooler are also presented. Direct evaporative cooling is restricted by atmospheric conditions. The outlet air conditions are theoretically determined at different ambient temperatures and relative humidities. Equations for the determination of the outlet air temperature and relative humidity are derived from Psychrometric relations. The equations cover a relative humidity range between 0–100 % and a temperature range between 10–60 oC. The influence of the cooling efficiency of the direct evaporative cooler is considered. The equations yield results that agree closely with values given by existing Psychrometric charts.