A 2 x 2 m flat plate solar collector for domestic hot water heating is shown in the figure. The incident solar radiation on the glass cover, which transmits 90% of the incident flux, is 750 W/m². Water flows through the tubes soldered to the backside of the absorber plate, entering at a temperature of 25°C. The temperature of the glass cover is 27°C, and it radiates heat with an emissivity of 0.92 to the sky at-50°C. Additionally, the glass cover losses heat by convection to air at 20°C flowing over its surface at 30 km/h. Assume that the radiation heat transfer between the absorber plate and glass cover and the heat transfer through the back and sides of the collector is negligible. Circulating Pump Collector Panels Thermostat Control Hot Water Cold Water Hot Water → Storage Tank with Electric or Gas Back-up ← Cold Water Air Flow O Fig. 1: Solar water heating system (left). Details of the collector panels (right). Air Space 0. O Insulation Nu, = 0.036Pr¹/3 (Re0.8-23200) The properties of air are given as follows: A. Start with the energy balance equation and determine the net solar energy Qu delivered by the absorber plate to the water in the tubes. 316.75 W/m^2 Determine the annual electricity and cost savings to this family due to the solar collector. For a turbulent flow over a flat plate, the Nusselt number is given as follows: B. Calculate the collector efficiency ne defined as the ratio of useful energy transferred to the water in the tubes to the solar energy incident on the collector. 43.7% C. Calculate the outlet temperature of the water Two if its flow rate through the collector is 0.02 kg/s. The specific heat of the water is 4.179 kJ/(kg K). 40.69°C D. The solar collector provides the hot water needs for a family for seven months except for five months of the winter season, which a resistance heater can supply. The cost of electricity is $0.13/kWh, and the efficiency of the electric heater can be taken to be 93% considering heat losses from the system. Glass Cover Absorber Plate Tubing for Fluid k = 0.0296 W/m.K, v = 16 x 106 m²/s, Cp = 2470 J/kg.K, Pr = 0.71

A 2 x 2 m flat plate solar collector for domestic hot water heating is shown in the figure. The incident solar radiation on the glass cover, which transmits 90% of the incident flux, is 750 W/m². Water flows through the tubes soldered to the backside of the absorber plate, entering at a temperature of 25°C. The temperature of the glass cover is 27°C, and it radiates heat with an emissivity of 0.92 to the sky at-50°C. Additionally, the glass cover losses heat by convection to air at 20°C flowing over its surface at 30 km/h. Assume that the radiation heat transfer between the absorber plate and glass cover and the heat transfer through the back and sides of the collector is negligible. Circulating Pump Collector Panels Thermostat Control Hot Water Cold Water Hot Water → Storage Tank with Electric or Gas Back-up ← Cold Water Air Flow O Fig. 1: Solar water heating system (left). Details of the collector panels (right). Air Space 0. O Insulation Nu, = 0.036Pr¹/3 (Re0.8-23200) The properties of air are given as follows: A. Start with the energy balance equation and determine the net solar energy Qu delivered by the absorber plate to the water in the tubes. 316.75 W/m^2 Determine the annual electricity and cost savings to this family due to the solar collector. For a turbulent flow over a flat plate, the Nusselt number is given as follows: B. Calculate the collector efficiency ne defined as the ratio of useful energy transferred to the water in the tubes to the solar energy incident on the collector. 43.7% C. Calculate the outlet temperature of the water Two if its flow rate through the collector is 0.02 kg/s. The specific heat of the water is 4.179 kJ/(kg K). 40.69°C D. The solar collector provides the hot water needs for a family for seven months except for five months of the winter season, which a resistance heater can supply. The cost of electricity is $0.13/kWh, and the efficiency of the electric heater can be taken to be 93% considering heat losses from the system. Glass Cover Absorber Plate Tubing for Fluid k = 0.0296 W/m.K, v = 16 x 106 m²/s, Cp = 2470 J/kg.K, Pr = 0.71

Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)

8th Edition

ISBN:9781305387102

Author:Kreith, Frank; Manglik, Raj M.

Publisher:Kreith, Frank; Manglik, Raj M.

Chapter8: Natural Convection

Section: Chapter Questions

Problem 8.33P

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