Analytical and Experimental Investigation to Determine the Variation of Hottel–Whillier–Bliss Constants for a Scaled Forced Circulation Flat-Plate Solar Water Heater

2015 ◽  
Vol 137 (5) ◽  
Author(s):  
U. C. Arunachala ◽  
M. Siddhartha Bhatt ◽  
L. K. Sreepathi
Keyword(s):  
Mass Flow Rate ◽  
Heat Loss ◽  
Mass Flow ◽  
Flow Rate ◽  
Loss Coefficient ◽  
Absorber Plate ◽  
Forced Circulation ◽  
Solar Water ◽  
Scale Thickness ◽  
Overall Heat Loss Coefficient

Fixed tilt flat-plate solar thermal collectors, popularly known as solar water heaters, still remain as one of the most interesting technologies for utilization of solar energy. The system performance deteriorates due to scaling because of the continuous use of hard water as feed water. The present study deals with the experimental and analytical approach to determine the variation of Hottel–Whillier–Bliss (H–W–B) constants (which compactly represent the efficiency characteristics of a solar water heater) due to variation in solar power input and degree of scaling in case of forced circulation system (FCS) without considering the variation of input power to the circulating pump. Indoor tests are performed with a copper tube to investigate the flow characteristics. This forms a part of conventional FCS, in place of the usual nine-fin tube array in a full-fledged collector. In indoor tests, electrical heating is favored to simulate solar radiation level. Various energy parameters are determined and compared by incorporating the developed numerical code FLATSCALE. Variation between experimental and analytical mass flow rate, overall heat loss coefficient, and H–W–B constants with simulated solar radiation level is plotted. In scaled condition, the drop in instantaneous efficiency is due to both scale thickness and reduced water flow rate. Scale thickness acts as an additional thermal conductive resistance between absorber plate and flowing water. Overall heat loss coefficient increases as absorber plate temperature is high during reduced flow rate. The maximum deviation observed is 21.68% in mass flow rate, 14.64% in absorber plate mean temperature, 7.86% in overall heat loss coefficient, and 12.04% in instantaneous efficiency. Compared to a clean tube, a highly scaled tube of 3.7 mm scale thickness indicates a drop of 4.76% in instantaneous efficiency and 40.28% in mass flow rate. It is concluded that the growth of scale in FCS does not affect the instantaneous efficiency significantly because of the margin in heat carrying capacity of water in spite of high drop in the flow rate.

Analytical and Experimental Investigation to Determine the Variation of H-W-B Constants for a Scaled Forced Circulation Flat Plate Solar Water Heater

2013 ◽  
Author(s):  
Arunachala Chandavar ◽  
Siddhartha Bhatt ◽  
Sreepathi Krishnamurthy
Keyword(s):  
Mass Flow Rate ◽  
Heat Loss ◽  
Mass Flow ◽  
Flow Rate ◽  
Circulation System ◽  
Absorber Plate ◽  
Forced Circulation ◽  
Solar Water ◽  
Scale Thickness ◽  
Overall Heat Loss Coefficient

Fixed tilt flat plate solar thermal collectors, popularly known as solar water heaters still remain as one of the most interesting technologies for utilization of solar energy. The system performance deteriorates due to scaling because of continuous use of hard water as feed water. The present study deals with the experimental and analytical approach to determine the variation of H-W-B (Hottel–Whillier–Bliss) constants (which compactly represent the efficiency characteristics of a solar water heater) due to variation in solar power input and degree of scaling in case of forced circulation system without considering the variation of input power to the circulating pump. Indoor tests are performed with a copper tube to investigate the flow characteristics. This forms a part of conventional forced circulation system, in place of the usual nine-fin tube array in a full fledged collector. In indoor tests, electrical heating is favored to simulate solar radiation level. Various energy parameters are determined and compared by incorporating the developed numerical code FLATSCALE. Variation between experimental and analytical mass flow rate, overall heat loss coefficient, H-W-B constants with simulated solar radiation level are plotted. In scaled condition, the drop in instantaneous efficiency is due to both scale thickness and reduced water flow rate. Scale thickness acts as an additional thermal conductive resistance between absorber plate and flowing water. Overall heat loss coefficient increases as absorber plate temperature is high during reduced flow rate. The maximum deviation observed is 21.68 % in mass flow rate, 14.64 % in absorber plate mean temperature, 7.86 % in overall heat loss coefficient and 12.04 % in instantaneous efficiency. Compared to a clean tube, a highly scaled tube of 3.7 mm scale thickness indicates a drop of 4.76 % in instantaneous efficiency and 40.28 % in mass flow rate. It is concluded that the growth of scale in forced circulation system does not affect the instantaneous efficiency significantly because of the margin in heat carrying capacity of water inspite of high drop in the flow rate.

Scaling Effect of Direct Solar Hot Water Systems on Energy Efficiency

2010 ◽  
Vol 132 (4) ◽  
Author(s):  
U. C. Arunachala ◽  
M. Siddhartha Bhatt ◽  
L. K. Sreepathi
Keyword(s):  
Heat Transfer ◽  
Energy Efficiency ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Transfer Rate ◽  
Water Systems ◽  
Hot Water ◽  
Forced Circulation ◽  
Scale Thickness

Scale formation in risers and header of direct solar hot water systems is a problem in places where hard water is being used. In this paper, the effect of scaling on energy efficiency indices such as instantaneous efficiency, mass flow rate, and overall heat loss coefficient are quantified by Hottel–Whillier–Bliss equation in the case of thermosiphon and forced circulation systems. The effect of scaling on mass flow and heat transfer rate for both the systems are quantified with experimental validation. Experimentally found mass flow rate is 50% of the analytical mass flow rate for a clean riser and agrees 99% for the case of riser with 3.75 mm scale thickness. This is due to the extreme change in pressure gain in the narrow region. Scale mapping is done for the entire solar hot water system to study the nature of scale growth. The complete footer and nine risers for the length of 150 mm from footer are free from scaling in axial and radial direction. This is due to the low water temperature in the region. The major portion of header and risers for the length 180 mm from the header are completely blocked due to maximum temperature of water in that region. A scale prediction model is brought out based on the experimentally observed scaled water heaters in the field. It reveals that the major parameters to be considered for the correlation are water total hardness and calcium hardness. It is seen in the thermosiphon system that the mass flow rate decreased by scaling affects energy efficiency more than that caused by the heat transfer rate. The scaling effect is more predominant in thermosiphon systems than in forced circulation systems. The analytical study reveals a drop in instantaneous efficiency of 39.5% in thermosiphon system and 7.0% in the case of forced circulation system for the scale thickness of 3.75 mm. The difference between mass flow rate in scaled and unscaled condition is less in forced circulation but much higher in thermosiphon system.

scholarly journals Heat loss from hot water flowing in a copper pipe insulated using air enclosed with a PVC pipe

2018 ◽  
Vol 8 (1) ◽  
Author(s):  
A. Albayani ◽  
M. Mirmanto ◽  
S. Syahrul
Keyword(s):  
Mass Flow Rate ◽  
Heat Loss ◽  
Mass Flow ◽  
Flow Rate ◽  
Test Section ◽  
Hot Water ◽  
Fluid Temperature ◽  
Copper Pipe ◽  
Pvc Pipe ◽  
Bare Copper

This paper presents investigations of heat loss from hot water flowing in an insulated copper pipe. Investigations were performed to know the heat loss from a copper pipe insulated using air enclosed with a PVC pipe. The fluid temperature used was kept at approximately 75°C in the entrance and its mass flow rate was around 12 g/s. The nominal copper pipe diameter was 6.35 mm; while the diameters of the PVC pipe were ranging from 12.7 mm to 5.08 mm. The length of the test section was approximately 3000 mm. The results show that the biggest heat loss is found using the bare copper pipe. When the copper pipe is insulated using air enclosed with a PVC pipe, the heat loss decreases with the increased PVC pipe diameters. The trend of the heat loss agrees with the critical insulation diameter theory.

Efficiency and heat loss analysis of honeycomb receiver varying air mass flow rate and beam width

2019 ◽  
Vol 137 ◽  
pp. 1027-1040 ◽  
Author(s):  
Mitsuho Nakakura ◽  
Koji Matsubara ◽  
Selvan Bellan ◽  
Tatsuya Kodama
Keyword(s):  
Mass Flow Rate ◽  
Heat Loss ◽  
Mass Flow ◽  
Flow Rate ◽  
Beam Width ◽  
Air Mass ◽  
Loss Analysis

Influence of absorber plate shape factor and mass flow rate on the performance of the PVT system

2019 ◽  
Vol 156 ◽  
pp. 692-701 ◽  
Author(s):  
Harendra Pal Singh ◽  
Aayush Jain ◽  
Arvind Singh ◽  
Swati Arora
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Shape Factor ◽  
Absorber Plate ◽  
Plate Shape

scholarly journals Heat loss from hot water flowing in a copper pipe insulated using air enclosed with a PVC pipe

2018 ◽  
Vol 8 (1) ◽  
pp. 1
Author(s):  
A. Albayani ◽  
M. Mirmanto ◽  
S. Syahrul
Keyword(s):  
Mass Flow Rate ◽  
Heat Loss ◽  
Mass Flow ◽  
Flow Rate ◽  
Test Section ◽  
Hot Water ◽  
Fluid Temperature ◽  
Copper Pipe ◽  
Pvc Pipe ◽  
Bare Copper

This paper presents investigations of heat loss from hot water flowing in an insulated copper pipe. Investigations were performed to know the heat loss from a copper pipe insulated using air enclosed with a PVC pipe. The fluid temperature used was kept at approximately 75°C in the entrance and its mass flow rate was around 12 g/s. The nominal copper pipe diameter was 6.35 mm; while the diameters of the PVC pipe were ranging from 12.7 mm to 5.08 mm. The length of the test section was approximately 3000 mm. The results show that the biggest heat loss is found using the bare copper pipe. When the copper pipe is insulated using air enclosed with a PVC pipe, the heat loss decreases with the increased PVC pipe diameters. The trend of the heat loss agrees with the critical insulation diameter theory.

scholarly journals Drying of mint leaves in forced convection solar dryer

2019 ◽  
Vol 23 (6 Part B) ◽  
pp. 3941-3949
Author(s):  
Munusamy Suresh ◽  
Ponnusamy Palanisamy ◽  
Kumar Senthil
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Work Performance ◽  
Drying Process ◽  
Performance Study ◽  
Absorber Plate ◽  
Forced Air ◽  
Drying Efficiency ◽  
Iron Tube

In this present work, performance study on drying mint leaves under the metrological conditions. Intensity of radiation falls on the absorber plate which transfers heat to forced air-flow inside the galvanized iron tube. Drying experiment carried out with 1 kg of mint leaves taken for drying process under the different mass-flow rate of 0.75 m/s and 1.25 m/s in serpentine flow of air. Performance of the collector and drying efficiency were 30.33% and 1.63% in first day at 0.75 m/s mass-flow rate and in the second day collector, the drying efficiency were 29.41% and 1.89% at the mass-flow rate of 1.25 m/s. The mass-flow rate of air decreased with increasing collector and drying efficiency.

Experimental Study With Analytical Validation of Thermally Driven Flow in Risers of Solar Water Heaters Under Varying Scale Thickness and Heat Flux

2013 ◽  
Vol 136 (2) ◽  
Author(s):  
U. C. Arunachala ◽  
M. Siddhartha Bhatt ◽  
L. K. Sreepathi
Keyword(s):  
Flat Plate ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Electrical Power ◽  
Incident Radiation ◽  
Scale Thickness ◽  
Water Heaters ◽  
Power Inputs ◽  
Solar Water Heaters

This paper investigates the deterioration in the performance of thermosiphon flat plate solar water heaters (SWH) with water side scaling. The study presents the analytical and experimental variation of mass flow rate of water with scale thickness in risers of conventional solar flat plate water heater for different electrical power inputs (covering the full range of solar incident radiation up to 1 kW/m2). This information is extended further to determine the drop in efficiency characteristics represented by the Hottel–Whillier–Bliss (H–W–B) constants for full–fledged SWH. To simulate scaling in risers in the absorber plate of a SWH, an artificial method of coating has been used to create single pipe riser of different uniform scale thicknesses. Four such risers are created with scale thickness of 0 mm, 0.7 mm, 1.7 mm, 2.7 mm, and 3.7 mm. The observed drop in mass flow rate through the range of risers between 0 mm and 3.7 mm scale thickness is 58.5% for the thermal input power (supplied through electric heating) of 129.5 W (corresponding to a solar incident radiation of 980 W/m2). In comparison, the analytical results show a corresponding drop of 70.12%. A comparison of the coated riser with a cut tube of an actually scaled riser indicates excellent matching of thermal conductivity. The divergence between experimental and analytical mass flow rate in the case of a riser of the highest scale thickness, viz., 3.7 mm, is the lowest because of increased pressure gain in the flow region together with higher temperature than predicted by the general equation. The experimental data of various energy parameters from the single tube scaled riser studies are matching with analytical values for the different input electrical power levels (corresponding to the different solar radiation levels). As identical conditions are used in the experimental analysis, the results for risers of various scale thicknesses and electrical power inputs are applicable to corresponding full–fledged SWH.

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