Energy and exergy analysis of the transient performance of a qanat-source heat pump using TRNSYS-MATLAB co-simulator

In this study, the transient performance of a qanat source heat pump is investigated using a TRNSYS-MATLAB co-simulator. The water/ethylene glycol-to-air compression heat pump and the helical coil heat exchanger, which is used to inject heat to or to extract heat from the qanat water, are mathematically modeled in matrix laboratory (MATLAB), and then, coupled to transient systems simulation (TRNSYS) model to evaluate the system transient performance and calculate the heating and cooling loads of the case study building. Comparison of the performance of the qanat source heat pump with an air source heat pump showed that the coefficient of performance of the qanat source heat pump is at least 5% and at most 34% higher than that of the air source heat pump. By increasing the flow rate of the working fluid in the helical coil heat exchanger from 2 L/min to 8 L/min, the coefficient of performance of the qanat source heat pump increases at least 12% and at most 34.1%. The maximum increase in energy efficiency ratio and free energy ratio of the system by the similar increase in the flow rate is 46.4% and 24.8%, respectively. The exergy analysis of the qanat source heat pump reveals that the minimum and maximum exergy efficiency of the system is 32% and 85.5%, respectively. The findings also indicate that the most exergy destruction occurs in the condenser in heating mode and in the evaporator in cooling mode.

Review: Observation on CFD Analysis of ZnO and TiO2 Nanofluid with Oil and Ethylene Glycol in Square and Helical Coil Heat Exchanger

Helically coiled heat exchangers are globally used in various industrial applications for their high heat transfer performance and compact size. Nanofluids can provide the excellent thermal performance in helical coil heat exchangers. Research studies on heat transfer enhancement have gained serious momentum during recent years and have been proposed many techniques by different research groups [1]. A fluid with higher thermal conductivity has been developed to increase the efficiency of heat exchangers. The dispersion of 1-100nm sized solid nanoparticles in the traditional heat transfer fluids, termed as nanofluids, exhibit substantial higher convective heat transfer than that of traditional heat transfer fluids. Nanofluid is a heat transfer fluid which is the combination of nanoparticles and base fluid that can improve the performance of heat exchanger systems. In this present paper the efforts are made to understand that how to compare the heat transfer rate in Copper helically coiled tube and squared coiled tube heat exchanger using Zinc Oxide and Titanium Dioxide Nano fluid by studying research papers of various authors. Keywords: Helical Coil, Nano-fluid, Heat Exchanger, CFD, Pressure Drop, Temperature Distribution.

Primary energy efficiency assessment of a coil heat recovery system within the air handling unit of an operating room

Heat recovery systems installed in Air Handling Units (AHUs) are energy efficient solutions during disparate outdoor-to-indoor temperatures. However, they may be detrimental in terms of a primary energy balance when these temperatures get closer, due to the decrease in the thermal energy recovered compared to the global energy consumption required for their operation. AHUs in surgical areas have certain particularities such as their continuous operation throughout the year, the large airflows supplied and the strict exigencies on the supply air quality, avoiding any cross contamination. This work presents the measurements and analysis performed on a coil heat recovery (run-around) loop system installed in the AHU that serves a mixed-air ventilation operating room in a Hospital Complex. A primary energy balance is studied, including the thermal and electric energy savings achieved, considering the electric energy consumption by the recirculation pump and the additional power requirements of fans due to the pressure drop introduced. The obtained value is then used to predict the thermal energy savings achieved by the heat recovery system. Results are extrapolated to the Typical Meteorological Year to provide an order of magnitude of the primary energy and CO2 emissions saved through the operation of the coil heat recovery system.

Diagnostics of a Domestic Hot Water Storage Tank under Operating Conditions

This paper presents a new method for the diagnostics of a hot water storage tank under operating conditions. Depending on the operating point of the tank, the method enables determination of thermal conductivity coefficients of the coil heat exchanger, which allows us to determine the intensity of heat transfer between the transfer medium and water in the tank as well as of tank walls, which consequently enables determination of heat losses to the environment. Furthermore, the dynamic properties of the tank may also be determined by applying this method. The advantage of this method is possibility of analyzing changes in the material constants of the coil heat exchanger, tank walls, and dynamic properties of the tank as a function of mass flow of the medium supplying the coil heat exchanger. The possibility of determining coefficients of thermal conductivity as well as the inertia of tank and exchanger, based on temperature measurements acquired in operating conditions is a novelty in this paper. Knowing the variability of material constants and of dynamic properties of the tank as a function of medium flow rate allows multicriteria optimization to be performed which, with a conventional design of the tank, results in a reduction of up to 10% in the time taken to prepare domestic hot water.