Single-zone System Research Articles

A Review on Pressure Transient Analysis in Multilayer Reservoir: South Iraq Case Study

Multilayer reservoirs are currently modeled as a single zone system by averaging the reservoir parameters associated with each reservoir zone. However, this type of modeling is rarely accurate because a single zone system does not account for the fact that each zone's pressure decreases independently. Pressure drop for each zone has an effect on the total output and would result in inter-flow and the premature depletion of one of the zones. Understanding reservoir performance requires a precise estimation of each layer's permeability and skin factor. The Multilayer Transient Analysis is a well-testing technique designed to determine formation properties in more than one layer, and its effectiveness over the past two decades has been demonstrated. In order to conduct MTA, a combination of rate profiles derived from production data and transient rate and pressure measurements at multiple surface rates is necessary. Numerous experimental and analytic approaches to calculating multilayer characteristics, performance, and flow behavior in multilayer systems have emerged. This technology was implemented at the Zubair oil field in southern Iraq. In the last four years, the number of wells producing under saturation pressure has been increased in the Zubair oil field, particularly for the Mishrif and Zubair reservoirs. In the design of secondary and tertiary recovery, the study of the reservoir in the form of an individual layer to determine the pressure, permeability, and damage of each layer with commingled formation is important. This research describes previously available methods, factors that affect Multilayer Transient Analysis an economic indicator of Multilayer Transient Analysis and a case study

Benchmarking high performance HVAC Rule-Based controls with advanced intelligent Controllers: A case study in a Multi-Zone system in Modelica

The design, commissioning, and retrofit of heating, ventilation, and air-conditioning (HVAC) control systems are crucially important for energy efficiency. However, designers and control contractors adopt ad-hoc control sequences based on diffused and fragmented information; therefore, most of the existing control sequences are diverse and sub-optimal. ASHRAE Guideline 36 (GDL36), High-performance Sequences of Operation (SOO) for HVAC Systems, was thus developed to provide standardized and high-performance rule-based HVAC control sequences with the main focus on maximizing energy efficiency. However, only limited studies verify the performance of these high-performance rules-based control and most of these studies focus on the single-zone systems. In this Modelica-based simulation study, the high-performance rule-based control sequences from GDL36 were compared to the state-of-the-art intelligent controllers (i.e., optimization-based controller (OBC) and deep reinforcement-learning-based controller (DRLC)) in terms of the energy efficiency and thermal comfort. The performance evaluation was conducted in a medium-sized office building with a multi-zone Variable Air Volume (VAV) cooling system. The OBC and DRLC replaced the GDL36 airside supervisory level control loops. In other words, the optimal supply air temperature (SAT) and static differential pressure (DP) setpoints were determined by the optimization problems in OBC and trained control policy by DRLC. The OBC and DRLC were formulated to minimize the HVAC energy consumption and zone air temperature violation. The OBCs with different control intervals and DRLCs with different hyperparameters in the Proximal Policy Optimization (PPO) algorithm were exploited and fine-tuned. The simulation results show that the GDL36 has a comparable energy performance (within a 3% deviation) with DRLC in the cases with high or mild cooling loads. It also has a comparable energy performance (within a 3% deviation) with OBC in the case of a high cooling load. However, the case with GDL36 consumed 7% more energy in the testing shoulder period. For the thermal comfort metric, the GDL36 has slightly more zone air temperature violations in all testing scenarios compared to the two intelligent controllers. From this case study, we can conclude that the GDL36 has demonstrated its comparable performance in terms of energy efficiency and thermal comfort with the two intelligent controllers. The GDL36 airside SOO is good enough considering the complexity and tuning efforts of the intelligent controllers.

Low-Cost Conversion of Single-Zone HVAC Systems to Multi-Zone Control Systems Using Low-Power Wireless Sensor Networks.

This paper presents a novel approach to convert a conventional house air conditioning installation into a more efficient system that individually controls the temperature of each zone of the house through Wi-Fi technology. Each zone regulates the air flow depending on the detected temperature, providing energy savings and increasing the machine performance. Therefore, the first step was to examine the communication bus of the air conditioner and obtain the different signal codes. Thus, an alternative Controller module has been designed and developed to control and manage the requests on the communication bus (Bus–Wi-Fi gateway). A specific circuit has been designed to adapt the signal of the serial port of the Controller with the communication bus. For the acquisition of the temperature and humidity data in each zone, a Node module has been developed, which communicates with the Controller through the Wi-Fi interface using the Message Queuing Telemetry Transport (MQTT) protocol with Secure Sockets Layer / Transport Layer Security (SSL/TLS) certificates. It has been equipped with an LCD touch screen as a human-machine interface. The Controller and the Node modules have been developed with the ultra-low power consumption CC3200 microController of Texas Instruments and the code has been implemented under the TI-RTOS real-time operating system. An additional module based on the Raspberry Pi computer has been designed to create the Wi-Fi network and implement the required network functionalities. The developed system not only ensures that the temperature in each zone is the desired one, but also controls the fan velocity of the indoor unit and the opening area of the vent registers, which considerably improves the efficiency of the system. Compared with the single-zone system, the experiments carried out show energy savings between 75% and 94% when only one of the zones is selected, and 44% when the whole house is air-conditioned, in addition to considerably improving user comfort.

Uncertainty analysis of various CO2-Based tracer-gas methods for estimating seasonal ventilation rates in classrooms with different mechanical systems

Indoor air quality (IAQ) data of 220 classrooms in the Midwestern region of the US were measured during 2015–2017. During three seasons (fall, winter, and spring), indoor and outdoor CO2 concentrations of each classroom were measured under both occupied and unoccupied conditions. To calculate ventilation rates from the collected CO2 data, three main methods derived from the mass-balance equation were used: (1) steady-state; (2) decay rate; and (3) build-up. Since the uncertainty of the individual measurement parameter affects the accuracy or reliability of the calculated, an uncertainty analysis was performed for all three methods. The uncertainty of the estimated ventilation rates in relation to the volume of the classroom, indoor and outdoor CO2 levels, and estimated student CO2 emission rates were determined. The study shows that the steady-state method has the least uncertainty in ventilation rate calculations, while the decay and build-up methods had the lowest and highest values for ventilation rates, respectively. The results also show the estimated ventilation has a larger variance in single-zone systems than in multiple-zone systems. In field measurements, CO2 readings contribute to the largest portion of uncertainty for all three methods. Therefore, with CO2 as the tracer gas, improving the accuracy of CO2 measurement should receive the highest priority for study.

Z-Wave based Zoning Sensor for Smart Thermostats

Background/Objectives: This paper speaks about the design of a wireless sensor module that senses the temperature and humidity of a residential building. In most of the cases the temperature in a home is controlled by a single thermostat placed at a central location. Methods/Statistical Analysis: Few rooms might be hotter or cooler than the other. Hence, zoning systems are used to provide independent comfort for each zone. Each zone can have a sensor that detects the temperature and humidity of the zone. But, the current thermostats have a sensor onboard which detect temperature and humidity. Findings: This sensor output can be affected by the heat produced by other devices on the thermostat. The solution of this problem is a wireless sensor which detects the exact temperature of the zone. Based on these values the thermostat runs a predefined algorithm and maintains the required environment in each zone. On comparison with different wireless technologies like Zigbee, Wi-Fi, Bluetooth. Z-wave suits more for the above applications whose frequency is 900 MHz which is different from the crowded 2.4 GHz frequency band and Z-wave also has a higher range and battery life. This system has a wireless sensor module which talks to the thermostat using Z-wave wireless communication protocol. This system uses ARM based microcontroller for wireless sensor unit. The thermostat has a high end ARM based microprocessor and a display unit which shows the acquired temperature and humidity. Conclusion/Improvements: his design shows a wireless sensor module that is implemented for a single zone system. Improvement can be done on the design to develop a low power battery operated sensor module that can be implemented for a multi zone system.

Towards energy performance evaluation in early stage building design: A simplification methodology for commercial building models

The paper analyses the benefits of the application of energy analysis in the early-stage building design, in particular for large commercial buildings. The research highlights the barriers that prevent this early integration and finally proposes the development of a methodology tailored around the optimization of energy efficiency during early-stage design. In general, the research aims to identify (a) the accuracy obtainable through progressive simplifications of the building model, (b) the most significant building parameters with respect to the model result accuracy and (c) the maximum number of simplifications able to ensure the respect of time requirements dictated by early-stage building design and to maintain an acceptable level of correctness. Here, as detailed example of simplification process, a case study of a large multi-storey office building is modelled starting with a previous detailed simulation performed through EnergyPlus and Openstudio software. The detailed model is then analyzed and progressively simplified. At each progressive simplification step, a comparison with the detailed results is given in terms of building energy needs and power curves of the system. The analysis is performed based on three different system hypotheses: a single-zone system and a variable air volume system with and without humidity control. The quantitative differences between detailed and simplified model are analyzed to determine the quality of the results of the simplified model.

Evaluating the Need and Potential of Equipping North American Houses with Multi-Zone VAV Systems

To identify potential energy savings and improvements to thermal comfort in the Canadian residential sector, a survey on occupant behaviour and control of thermal environment was conducted from April-June 2009 in low-rise dwellings in Ontario, Canada. A total of 396 completed responses were received. Survey results show that approximately 20% of the respondents were not satisfied with their room temperature in the winter. Inadequate level of controllability to room temperature is perceived as the most serious problem. Problems associated with overheating during the winter and overcooling during the summer was also identified. Observations from the survey results helped identify the deficiencies of the heating equipments built today and suggest improvements should be made to increase the controllability of current systems. Thermal simulation was then conducted to identify the problems with single-zone systems commonly built today, and to investigate the potential retrofit alternative. Simulation results show that a multi-zone system can effectively mitigate the deficiencies suffered by existing systems and can drastically improve the energy performances of houses.

Multiple-zone HVAC: An Obsolete Template

ABSTRACT Multiple-zone central air handling systems are presently the dominant type of HVAC for large buildings. Despite that, they are obsolete. They are inherently incapable of providing a high level of comfort and good ventilation while operating with good energy efficiency. In addition, such systems make buildings vulnerable to infectious diseases, fire, and terrorism. These shortcomings are inherent; they are not merely practical problems that await clever solutions. The desirable alternative is single-zone systems. These can completely avoid or greatly reduce the problems of multiple-zone systems. Furthermore, the economics of single-zone systems are favorable in comparison with central systems. In order for the full potential of single-zone systems to be achieved, a new doctrine of HVAC design, called “optimized-function HVAC,” was presented internationally in 2005, with greater detail being added in later presentations. This doctrine is freely available, and the sources are given at the end of this article. Responsible HVAC designers will take the initiative to learn this optimized doctrine of HVAC design and bring it into practice as quickly as possible.

Aquifer Parameter Estimation for a Constant‐Flux Test Performed in a Radial Two‐Zone Aquifer

A patchy aquifer or an aquifer with a finite thickness skin can be considered as a radial two-zone aquifer system, which can be characterized by five parameters, i.e., the thickness of the first zone and four aquifer parameters including the transmissivity and storage coefficient for each of the first and second zones. This paper proposes an approach based on an analytical solution of a constant-flux pumping in a confined two-zone aquifer and the simulated annealing algorithm to determine the five parameters simultaneously. The estimated results for the five parameters are fairly good even assuming the aquifer as a single-zone system at the beginning of the data analysis. The estimated results indicate that the first-zone parameters are much more difficult to accurately identify than the second-zone parameters due to insufficient early-time data and high correlation of the sensitivities among the first-zone parameters. However, the problem of inaccurate results obtained at the first-zone can be significantly improved if more densely temporal drawdown measurements are used.

Measurement of ventilation and aerosol particles in buildings

The work described in the paper is concerned with the measurement of the flow of tracer gas and aerosol particles in rooms. Measurements were carried out in single- and two-zone systems using SF6 tracer gas and oil-smoke particles. Initial tests were carried out in a single-zone system using different arrangements of window opening. Results indicated that tracer-gas exchange rates were generally higher than particle exchange rates. This was due to the fact that the ventilation air entering the zone contained a significant concentration of particles but a negligible quantity of tracer gas. The exchange rates of tracer gas and smoke particles through a doorway were also measured in a two-zone system. The doorway coefficients of discharge were calculated using a theory based on the Bernoulli equation. The coefficients of discharge for the opening were in the range 0.4–0.96 for tracer gas measurements and 0.15–0.42 for smoke-particle measurements.