Hot Water Flow Rate Research Articles

Experimental investigation on thermal performance and economic analysis of cosine wave tube structure in a shell and tube heat exchanger

A novel design of tube structure with cosine wave is proposed in this study to investigate effects of wavy surface characteristics on enhancement of heat transfer in a shell and tube heat exchanger, experimentally. All experiments have been designed and carried out on water/water loops. Response Surface Methodology is used to investigate the optimization procedure. Four effective parameters of wavy starting length (0 mm ≤ b ≤ 120 mm), hot water flow rates (11 l/min ≤ Qc ≤ 19 l/min), cold water flow rates (7 l/min ≤ Qh ≤ 11 l/min) and wavy wavelength (0 mm ≤ λ ≤ 80 mm) in five levels was selected to obtain the maximum thermal performance factor. The results showed that the thermal performance factor reduces by increasing of the hot water flow rate. The thermal performance factor of wave tubes is found to be larger than that of smooth tubs. Optimizing of the procedure indicated that to maximize the thermal performance factor, the lower values of wave starting length and hot water flow rate, and higher values of cold water flow rate and a wavelength of 33.13 mm, must be selected. Also results show that the corrugating process is useful from economic analysis point of view.

Non-invasive estimation of domestic hot water usage with temperature and vibration sensors

Electric water heaters are responsible for a large portion of electricity consumption and water usage in the domestic sector. Smart water heaters alleviate the strain on the electricity supply grid and reduce water consumption through behavioural change, but the installation of in-line flow meters is inconvenient and expensive. A non-invasive water flow meter is proposed as an alternative. Non-invasive flow measurement is more common for high flow rates in the industrial sector than for domestic applications. Various non-invasive water measurement methods are investigated in the context of domestic hot water, and a combination of thermal- and vibration-sensing is proposed. The proposed solution uses inexpensive, easily installable, non-invasive sensors and a novel algorithm to provide the same flow measurement accuracy as existing in-line meters. The algorithm detects the beginning and end of water consumption events with an accuracy of 95.6%. Quantitative flow rate estimation was possible for flow rates greater than 5 L min−1 with an accuracy of 89%, while volumetric usage estimation had an accuracy of more than 93%. The algorithm limitations were applied to field data, revealing that water consumption could be detected with an error of less than 12% within the limitations of the proposed algorithm. The paper presents a successful proof of concept for a non-invasive alternative to domestic hot water flow rate measurement.

Shallow hot-water ice drill: Estimation of drilling parameters and testing

Shallow hot-water systems are well-known ice-drilling devices used to create holes for temperature measurements and monitoring of glacier dynamics, basal sliding, and englacial water-pressure. A shallow hot-water ice drill system designed at Jilin University is based on a commercial high-pressure washer, Kärcher HDS 6/14C, that can deliver water at a temperature in the range of 80–155° C, a flow of 4–10 L/min and a pressure as high as 14 MPa. The system also includes a mast with a sheave on the top and a reel with a 100-m long rubber hose; a 2-m long, 60-mm diameter drill stem; a control and measuring system; sleds; a submersible pump; a return hose; a water tank with an affiliate heating unit; and a small 2-kW generator. Theoretical estimations were performed to predict the rate of penetration and mean diameter of the melted borehole. Experiments with a shallow hot-water drill were carried out in an ice drill testing facility to determine the relationship between the rate of penetration/borehole diameter and the diameter and type of nozzle, hot water temperature, and flowrate. Under a hot water flowrate of 10 L/min with a temperature of 60° C, the 1.8-mm and 2-mm nozzles created 98–114-mm diameter boreholes at a penetration rate of 34–37 m/h, while a 2.5-mm nozzle produced a 146–156-mm borehole at rate of 26 m/h. The deviation between the experimental data and theoretical estimations did not exceed 7%.

Energetic evaluation of a double-effect LiBr-H2O absorption heat pump coupled to a multi-effect distillation plant at nominal and off-design conditions

This paper presents the experimental characterization of a double-effect absorption heat pump (DEAHP) using lithium bromide-water (LiBr-H2O) which recovers the low-energy latent heat from the last effect of a multi-effect distillation (MED) plant. The experimental facility is located at the Plataforma Solar de Almería (PSA) and the test campaign has been performed with the aim to find the best operating strategies that minimize the energy consumption and maximize the energetic efficiency of the DEAHP-MED system taking also into account the distillate production of the MED unit. For this purpose, the impact of the variation of the input variables by which the DEAHP-MED system can be controlled (MED inlet hot water flow rate, MED inlet hot water temperature, the live steam flow rate and the DEAHP cooling water flow rate) on the coefficient of performance (COP), the performance ratio (PR) and on the total distillate production, has been analysed in two different coupling schemes between the DEAHP and the MED unit (indirect and direct). The results revealed that in direct mode, the rise in the live steam flow rate has the greatest impact on the distillate production and the increase of the MED inlet hot water flow rate and the DEAHP cooling flow rate on the COP. In the indirect mode, the rise in the MED inlet hot water temperature was the most influential in both parameters. The maximum COP, distillate production and PR was 2.08 ± 0.34, 2.42 ± 0.07 m3/h, and 18.53 ± 1.94, respectively in the direct mode and 2.04 ± 0.39, 1.92 ± 0.11 m3/h, 16.67 ± 3.42, respectively in the indirect mode. Moreover, empirical correlations that forecast the PR and the distillate production as a function of the COP were developed from the characterization results and were validated statistically by the coefficient of determination (R2) and the adjusted R2Radj2.

Study on performance of horizontal single pass shell and multi-tube heat exchanger with baffles by air bubble injection

ABSTRACTThe single pass shell and multi-tube heat exchanger with double segmental baffles'’ performance improvement were experimentally investigated by two methods of air injection into shell side when an increase in air bubble created an effect in the corresponding values of shell and tube heat exchanger such as the overall heat transfer coefficient, effectiveness, NTU and the pressure loss. In the first method, air bubble injection into shell side was parallel to the cold water flow; also in the second method, air bubble injection into shell side was cross flow to the cold water with different air flow rates to calculate approximately the most favourable performance conditions. 1–6 LPM of air flow rates and 10–20 LPM shell side water flow rates were transformed with constant tube side hot water flow rate.

Exergy analysis of double tube heat exchanger for parallel flow arrangement.

This paper presents the analysis of exergy according to second law of thermodynamics for a double concentric tube heat exchanger experimentally. For this purpose to study the heat exchange process between two fluid mediums separated by a solid partition for parallel flow arrangement, an experimental setup was fabricated as per designed considered to measured data. In this considered double concentric tube heat exchanger, hot water and cold water flowing through inner and outer tube respectively and heat exchange takes place from hot fluid medium to cold fluid medium. Here the wall tube conductive resistance is assumed as negligible. The investigation was performed for mass flow rate of cold water ranging from 0.0326 kg/s to 0.572 kg/s and mass flow rate of hot water ranging from 0.016 kg/s to 0.479 kg/s. The effects of various parameters such as rate of entropy generation, number of entropy generation, effectiveness of heat exchanger, and losses of exergy are observed by exergy analysis. The governing equations have been employed to solve analytically for obtaining the energy and exergy analysis parameters. It is expected that this study might be helpful for further related work.

Comprehensive analysis of a multi-generation energy system by using an energy-exergy methodology for hot water, cooling, power and hydrogen production

In this study, an energy-exergy methodology was applied to achieve more precise conditions for hot water, cooling, power and hydrogen production via a proposed multi-generation system comprised of a geothermal based organic Rankine cycle, domestic water heater, absorption refrigeration cycle and proton exchange membrane electrolyzer. Furthermore, for evaluation of the proposed system performance, the effects of such key variables as brine temperature, turbine inlet temperature, generator temperature, brine mass flow rate and electrolyzer current density on the related efficiencies of energy and exergy for the whole system were investigated. For specified conditions, the results show that energy and exergy efficiencies of the entire system are calculated around 33.92% and 43.59%, respectively. Moreover, estimation of the exergy destruction rate in each system component indicated that the highest rate of exergy destruction occurred in the heat recovery steam generator (HRSG) with 16.65% of the total amount of exergy input to the system. And finally, net electrical power output, mass flow rate of hot water, cooling capacity and mass flow rate of hydrogen production are as follows: 816.7 kW, 7.06 kg/s, 1896 kW and 0.05g/s.

Experimental Investigation of Heat and Mass Transfer in Evaporative Heat Exchangers at Variable Operating Conditions

The evaporative heat exchanger has numerous applications in transferring heat. In this research an experimental study of the heat and mass transfer has been conducted on an experimental evaporative heat exchanger. The study involves the effect of cold water mass flow rate, hot water inlet temperature, air flow rate, injection holes diameter and horizontal distance between injection holes on the heat transfer, overall heat transfer coefficient, effectiveness and mass transfer. The results obtained indicate an increase of heat and mass transfer with the increase of hot water flow rate, hot water inlet temperature, air flow rate and injection holes diameter.

Experimental investigation of gas bubble diameter distribution in a domestic heat pump water heating system

A significant amount of national energy in the UK has been consumed in the residential sector mainly for space heating and domestic hot water production. Currently, gas boilers are mostly applied in the domestic water heating which contribute significantly to excessive CO2emissions and consumption of primary energy resources. The issues can be solved by popularizing heat pump systems that are attributable to higher performance efficiency than those of traditional gas boilers. Even so, the heat pump system performance can be further enhanced and improved if the dissolved gases in its hot water circuit can be efficiently discharged. To achieve this target, the bubble behaviors in the heat pump water heating system need to be extensively investigated. Based on a purposely built test rig of an air-water heat pump system, the effects of various heat pump hot water side parameters on gas microbubble diameters were measured and analyzed through different experimental conditions. The operational parameters include water flow rate, water flow pressure, system heating load and water flow dissolved gas saturation ratio. It is found from the measurements that the hot water flow rate is the dominate parameter which affects the average bubble diameter and bubble number distribution at different bubble sizes. The research outcomes can significantly contribute to the understanding of gas bubble behaviors at domestic heat pump water heating systems and thus the efficient way for the discharging of the associated dissolved gases.

A-37 住宅における湯の用途別適温・適流量に関する研究(その3) : アンケート調査および行動様式の分析

A-37 住宅における湯の用途別適温・適流量に関する研究(その3) : アンケート調査および行動様式の分析

Exergy analysis of a liquid desiccant evaporative cooling system

In this paper, a model of liquid desiccant evaporative cooling system is presented and simulated. The objective of this paper is to reveal the effects of various parameters on thermodynamic performance and to show the optimal range of those parameters. These results show that the system performance is strongly influenced by the hot water temperature, the flow ratio of air to solution and ambient air relative humidity, followed by the hot water flow rate. And the optimal range of each influencing factor is determined as follows: hot water temperature and the value of ma/ms are adopted to be about 75 °C and 1 kg⋅kg−1 respectively, while hot water flow rate will not be greater than 0.6 kg⋅s−1 and the range of the relative humidity of the atmosphere is wide. The analysis of the exergy efficiency ratio shows that the regenerator (REG), dehumidifier (DEH) and the enthalpy exchanger (EX) in the system are the weak parts of the system.

Experimental characterization of a multi-effect distillation system coupled to a flat plate solar collector field: Empirical correlations

In the last three decades, developments in desalination plants have been focused on the minimization of its energetic consumption and cost. Advancements include emerging technologies that make use of low grade thermal energy, like Multi-Effect Distillation (MED). The energy optimization of MED systems and their coupling with solar thermal technologies have been deeply investigated by the Solar Desalination Unit of the Plataforma Solar de Almería (PSA) through a solar desalination test facility consisting of a MED plant coupled to a static solar field. Recently, the previous solar field composed of compound parabolic concentrators (CPC) has been replaced by a new one with large-aperture flat plate collectors (FPC). In this work, an experimental characterization of the solar MED system under off-design conditions is presented and discussed. The efficiency of the FPCs’ solar field at several temperature levels for different climate conditions has been determined. Also, the influence of the variation of key parameters by which the MED plant is controlled (the inlet hot water flow rate (mhot) and temperature (Thot), the feed water flow rate (mf) and the condenser vapor temperature (Tc)) on the freshwater production and performance ratio (PR), were analyzed with an experimental campaign of 82experiments. The results obtained were used to fit polynomial expressions, validated statistically, that predict the distillate yield and the PR for different operation strategies. The experimental characterization of the desalination plant revealed that the rise in the Tc has the highest impact in the thermal efficiency of the MED unit, and the rise in the mf has the greatest influence on the distillation production. Moreover, from the analysis of the coupling of the MED plant with the solar field it was found that the thermal storage has an autonomy of up to 6h when the MED works with hot water at 65°C, which allows the plant to continue the operation even in transient periods (presence of clouds). Also, from a theoretical annual study for the solar MED system, it was found that the annual solar fraction ranges from 30.7% to 42.4%, which leads to an annual distillate production between 6701m3 and 11,314m3, respectively.

Performance Analysis of Three Fluid Heat Exchanger Used in Solar Flat Plate Collector System

Abstract In the present study, the thermal performance of a three fluid heat exchanger (TFHE) used in solar flat plate collector system is studied. The TFHE is an improved version of double pipe heat exchanger, where a helical tube is inserted between two concentric straight tubes for better performance. This paper presents a new technique of simultaneous air and water heating in TFHE using solar energy. The heating cost can be minimised considerably by supplying the hot water or thermal fluid from a solar flat plate collector through the helical tube of TFHE to heat incoming cold air and water in the inner most pipe and outer annulus. The TFHE is investigated experimentally and validated by comparing the result of experimental approach with literature. Decent agreements between the experimental and literature values are observed. The purpose of this study is to determine the effect of Reynolds number and Dean number on performance of the TFHE in steady-state for both flow configurations. The overall heat transfer coefficients, U o,h-n varies directly and effectiveness, ɛ h-n varies inversely with hot water volume flow rate, however hot water flow rate have least or no effect on coil side Nusselt number, Nu h . The effect of inner Dean Numbers on overall heat transfer coefficients, U o,h-n and effectiveness, ɛ h-n is negligible in parallel flow configuration, however is appreciable in counter flow configuration.ommittee of RAAR 2016.

An analytical method for defining the pump`s power optimum of a water-to-water heat pump heating system using COP

This paper analyzes the energy efficiency of the heat pump and the complete heat pump heating system. Essentially, the maximum of the coefficient of performance of the heat pump and the heat pump heating system are investigated and determined by applying a new analytical optimization procedure. The analyzed physical system consists of the water-to-water heat pump, circulation and well pump. In the analytical optimization procedure the "first derivative equal to zero" mathematical method is applied. The objective function is the coefficient of performance of the heat pump, and the heat pump heating system. By using the analytical optimization procedure and the objective function, as the result, the local and the total energy optimum conditions with respect to the mass flow rate of hot and cold water i. e. the power of circulation or well pump are defined.

Characteristics of heat transfer and pressure drop in a chevron-type plate heat exchanger with Al2O3/water nanofluids

In this study, heat transfer and pressure drop characteristics have been experimentally investigated by using Al2O3-water nanofluids in the chevron-type plate heat exchanger. The purpose of the experiments was to determine the heat transfer coefficient and pressure drop for different flow rates of 90, 120, 150, 180, 240, and 300 kg/h and different volume concentrations of 0.25%, 0.5%, 0.75%, and 1% of the nanofluids. The Nusselt number of the nanofluids increased with the increasing volume concentration and flow rate at constant hot water flow rate and constant inlet temperatures. The increase in the Nusselt number is 42.4% when compared to distilled water at the maximum volume concentration and Reynolds number (600 ? Re ? 1900) in the nanofluids-plate heat exchanger. It has been concluded that nanofluids enhanced the heat transfer significantly and pressure drops at the maximum volume concentration and the Reynolds number increased by between 6.4% and 8.4% compared to distilled water.

Experimental performance study on a dual-mode CO2 heat pump system with thermal storage

Performances of a water-source CO2 heat pump coupled with hot and cold thermal storage were investigated experimentally in this study. This combined system was tested by controlling compressor frequency, expansion valve opening, and hot and cold circulated water flow rates. Experimental results shows that higher compressor frequency leads to a shorter energy charging time and a higher overall coefficient of performance (COP) of the combined system during the charging process. Expansion valve opening affects the COPs significantly but affects the thermal stratification in thermal storage tanks slightly. Low hot and cold water flow rates lead to the good thermal stratification in storage tanks, which is beneficial for the overall COP of the combined system during the charging process, although high water flow rates are beneficial for the transient COP of heat pump at the beginning of the charging process. The overall COP reaches maximum when the hot and cold water flow rates were set as 0.1m3/h and 0.2m3/h respectively at the compressor frequency of 50Hz and at the expansion valve opening of 330 pulses. Based on the test data, the correlations of COP with the outlet water temperature of thermal storage tanks were developed for further optimizing this combined system.

Potential of a dual purpose solar collector on humidification dehumidification desalination system

An experimental investigation on a humidification dehumidification (HDH) desalination system integrated with a dual purpose solar collector (DPSC) is reported in this work. The DPSC is used to simultaneously heat the water and air needed for the distillation process. Air flows over the top surface of the absorber plate and the water flows through the riser tubes, attached in the bottom side of absorber plate. The heated air and water from the collector is supplied to the humidifier, where the air gets humidified and moves towards dehumidifier for condensation. The performance of the system is analyzed by providing semi circular turbulators (convex and concave) in the air flow field. The system ability is investigated by varying the flow rate of air, hot water in humidifier and cooling water in dehumidifier. The system distillation capacity enhances with the air and water temperature and flow rate of air, hot water and cold water. The highest productivity of 12.36, 14.14 and 15.23kg/m2.day is collected for the without turbulators, convex and concave turbulators in absorber plate respectively. The overall efficiency of the system reaches the value of 67.6% with the concave turbulators in the DPSC.

Experimental investigation of an air heating system using different types of heat exchangers incorporated with an evacuated tube solar collector

In this article, the thermal performance of a solar air heating system is experimentally investigated. In this system, an evacuated tube solar water heater is connected to a heat exchanger with connecting pipes. The evacuated tubes are used to produce hot water. This hot water flows to the heat exchanger through connecting pipes, the flow of hot water occurs due to thermosyphon phenomenon. Hot air is generated by passing ambient air through the heat exchanger. Three different types of heat exchanger viz. type‐I, type‐II and type‐III have been used. The height of the heat exchangers has been varied from 1050 mm to 1800 mm to evaluate the effect of height variation on the natural circulation flow rate of hot water. The maximum measured temperature difference between the hot air and the ambient air achieved was 10.7°C which was obtained with the heat exchanger type‐II at the height of heat exchanger from ground level of 1550 mm. © 2016 American Institute of Chemical Engineers Environ Prog, 36: 232–247, 2017

Experimental and Computational Fluid Dynamics Studies on Dehumidifier in a Combined Cooling and Desalination Plant

Humidification–dehumidification (HDH) desalination is a simple technique to produce desalinated water from saline water. Dehumidifier is a key component in the HDH system, which influences the desalination yield. In the current work, a three-dimensional multiphase numerical simulation study is carried out on third dehumidifier alone to evaluate its performance using computational fluid dynamics (CFD) code. The simulation result is validated with experimental readings, and it is found that there exists a very close agreement between the predicted and the experimental readings. The key parameters influencing the dehumidifier performance are chilled water temperature, humid air temperature, and volume fraction. Experiments are carried out on the combined two stage HDH plant at different hot water temperature and flow rates. A detailed study of dehumidification process is carried out using ansys cfx 15.0 tool by solving the governing equations, namely, mass, momentum, and energy, with turbulence modeled through shear stress transport (SST) k–ω model of closure. Multiphase is solved using a free-surface multiphase model. The measured average cooled air temperature and relative humidity (RH) at the exit of third dehumidifier are 21 °C and 67%. The desalinated water produced at a hot water flow of 100 LPH is found as 2205 ml/h from the experiments. The CFD results are deviated by 0.41%, 6.45%, and −0.70% with that of experimental results at the dehumidifier for air temperature, velocity, and chilled water temperature, respectively.

Actuator Fault Tolerant Control Based on a MIMO-MPC: Application in a Double-Pipe Heat Exchanger

In this work, an experimental fault tolerant control (FTC) implementation is presented. The FTC is based on a multi-input multi-output (MIMO) model predictive control (MPC). The aim of the FTC is to keep on operating a double-pipe counter-current heat exchanger even if the main actuator of the heat exchanger is stuck open. To develop the FTC, an adaptive observer was implemented in order to design a fault detection and isolation (FDI) system. In the FDI system, the cold and hot water flow rate estimations by the adaptive observer are compared to the control signals provided by the MPC. The results of the implementation of the FTC using a MIMO model predictive control were compared to the results obtained in a previous work which was developed using model-following control.