Abstract.This work presents the experimental evaluation of the energy performance of a modified single-stage CO 2 transcritical refrigeration plant with an internal heat exchanger (IHX) based on vapour injection in suction line. This modification, which is only applicable to refrigeration plants with an expansion process divided in two stages with a liquid receiver between them, consists of extracting saturated vapour from the liquid receiver in order to: decrease the vapour quality at the evaporator inlet, and reduce the superheating degree at the compressor suction by means of the expansion and following injection of the extracted refrigerant. Three different injection points have been evaluated experimentally: before the IHX, after the IHX and just before the suction chamber of the compressor. The experimental measurements show that the cooling capacity and COP can be enhanced in 9.81% and 7.01%, respectively. Furthermore, a reduction in the discharge temperature of the compressor up to 14.7ºC has been measured inside the evaluation range.
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Abstract:The paper presents the analysis of the energy performance of an air vortex cooling tube under variations of the air inlet properties, with three independent experimental tests validated through the energy balance in the device.The experimental analysis includes the following variations of the input conditions: First, the effect of the air inlet pressure to the vortex tube, focused on the analysis of temperature variations in the output cold stream and in the cooling capacity when the cold flow fraction varies. Second, we studied air inlet temperature variations to the vortex tube under different cold flow fractions, which is an analysis not found in the literature. And finally, is studied the performance of the vortex tube when the insulation is provided or in absence of insulation.
Productivity index (PI) reduction is a recognized phenomenon in oil and gas production to the extent that production becomes uneconomic. Productivity index (PI) decrease may be caused by several factors arising from reservoir, completion, and operational issues. The reservoir-related factors include compaction, fines migration, pressure support and multi-phase fluid flow. The completion-related issues arise from frac-pack geometry and stress-sensitivity of proppant conductivity. Finally, operational issues such as pressure drawdown at the sandface and induced flux (the movement of fluids across the completion) may also play a large role in PI degradation. Understanding the interactions of different parameters controlling the PI behavior and the resultant well performance is paramount for maximizing the ultimate recovery and net-present value or NPV. PI modeling may offer several challenges because it involves non-unique solutions for reservoirs and near-wellbore and well-completion status, in addition to manual data entry subject to human errors, uncertainties in reservoir parameters, and poor quality field data.
This study presents a workflow for modeling well PI degradation for an over-pressured gas/condensate reservoir in deep offshore Gulf of Mexico. An automated procedure was tailored and applied to match production history by adjusting both the reservoir and well completion parameters. Among the reservoir parameters considered were horizontal stresses, rock compressibility, absolute permeability, relative-permeability endpoints and curvature, porosity, stress-sensitive permeability and porosity. The well completion parameters included fracture length, height, width, conductivity, and stress. A "Tabu Scatter Search" optimizer engine (April et al, 2003) selected the optimal values of a set of input parameters to minimize the objective function, i.e. the error between the measured and calculated PI values.
Both reservoir and well completion parameters contributing to PI degradation were identified, and compared to those obtained by alternate methods. The relative and combined contributions of stress-sensitive reservoir compressibility, permeability, porosity, and fracture conductivity all helped understand well performance and guide decisions towards optimum well operating envelope.
This study presents the environmental impact assessment of an absorption heat transformer designed to recover 1 kW of thermal energy from each 2 kW of waste heat supplies. The net contribution of the heat transformer is a load avoided of 0.665 kg CO2 equivalents; the recovery process avoids 0.729 kg CO2 equivalents and the major contribution to the environment impacts is the pumping process with 0.0437 kg CO2 equivalents for each 1 kWh recovered. The study results show that absorption heat transformer is a good environmental option because it produces useful energy from waste heat and the final result is an environmental impact diminution.
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