Photosynthesis, as it occurs in the leaves of a green plant, involves the transport of carbon dioxide
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Fundamentals of Heat and Mass Transfer
- For stationary applications, mass and volume considerations for a fuel source are much less important than they are for use in transportation. It therefore may be the most reasonable to sacrifice compactness to minimize requirements for expensive advanced technologies. Consider a plan to provide power to a small city with a population of 100,000, using hydrogen fuel cells with an efficiency of 60%. The average net per-capita power consumption is 6 kW of electricity, heat, and power for an electric vehicle. (a) Calculate the volume of hydrogen needed to provide the city's energy for one month if the hydrogen is stored at a (relatively low) pressure of 1 MPa. (b) If the city has a land area of 100 km2, what fraction of this area would need to devoted to hydrogen storage if the storage tanks were vertical cylinders 3 m in diameter and 5 m high and were packed tightly together in a square array?arrow_forwardA stand-alone photo voltaic (PV) system for operating a street light consists of a PV array, storage battery, controller and DC-AC inverter o which an LED bulb of 20 Watts is connected. The PV array consists of 2 modules each containing 36 single crystal Si cells, each of 10 cm diameter. Conversion efficiency of the PV cells is 11%. The battery has an efficiency of 0.82 both while charging and discharging. DC-AC inverter has an efficiency of 0.85 while discharging the energy. The PV array receives solar radiation of approximately 22,600 kJ/m? per day. i. If the controller switches on the street light at 18:00 hrs, find the time when the street light would be switched off because of complete battery discharge. Calculate the energy stored in the battery on this day. ii.arrow_forward6arrow_forward
- The earth receives 1.8 x 10 14 kJ/s of solar energy. What is the mass of solar material is converted to energy over a 24-hr period to provide the daily amount of solar energy to the earth? What mass of the coal would have to be burned to provide the same amount of energy? (Coal releases 32 kl of energy per gram when burned).arrow_forwardThe wear resistance of a steel gear is to be improved by hardening its surface. This is to be accomplished by increasing the carbon content within an outer surface layer as a result of case-hardening. The carbon is to be supplied from an external carbon-rich gaseous atmosphere at an elevated and constant temperature. The initial carbon content of the steel is kept as a constant and is 0.20 wt%. The surface concentration is to be maintained at 1.00 wt%. For this treatment to be effective, (a) What diffusion process can be assumed in this situation? (b) What type of solid solution is it for the steel after diffusion? (c) What is the diffusion coefficient of carbon in steel if the heat treatment is conducted at 800 ℃? (d) How long will it take to achieve a carbon content of 0.60wt% at a position 0.75 mm below the surface at 1050 ℃?arrow_forwardTrue or False? Justify your answer. A. In a rectangular drug delivery device that consists of a drug reservoir and a diffusion barrier made of a polymer gel, the steady state diffusion (mass transfer) rate through a barrier of thickness 1 cm was found to be 20 mg/day. If the barrier thickness were to be doubled keeping the reservoir drug concentration the same, the mass transfer rate would be 10 mg/day. B. In a spherical drug delivery device consisting of a core reservoir surrounded by a polymer gel barrier, the steady state diffusion (mass transfer) rate through a barrier of thickness 1 cm was found to be 20 mg/day. If the barrier thickness were to be doubled keeping the reservoir drug concentration the same, the mass transfer rate would be 10 mg/day.arrow_forward
- The global average sensible heat flux is 17 W/m2. Use the following information to estimate the latent heat flux in units of W/m2. The annual global precipitation amount is about 520×1012 m3/yr. The latent heat of vaporization for water is 2.5×103 kJ/kg and the radius of the Earth is 6400 km. What is the global annual average latent heat flux?arrow_forwardA bioengineer working at chemical company intends to dry an insoluble wet granular material in a pan 0.6 x 0.6 m and 3 cm deep. The material is at the same dept in the pan, whereas the sides and the bottom can be considered to be insulated. Heat transfer is by convection from an air stream flowing parallel to the surface at a velocity of 10 m/s. The air is at 65.6°C and has a humidity of 0.010 kg H2O/kg dry air. Calculate the rate of drying for constant-rate periodarrow_forwardProblem: PH 54 A parking lot is contaminated with 5-um particles of Cs-137 to a value of 500 Bq/cm². Emergency responders set up a command post in the parking lot, and work for 8 hours. Determine: a. the inhalation effective dose due to resuspension, with a resuspension factor of 2 x 10° /cm. b. the external effective dose due to direct irradiation.arrow_forward
- ANSWER THERMOFLUIDS QUESTIONSarrow_forwardسحهثعقهكسنيتلتولوظزؤزظarrow_forwardThe wear resistance of a Steel shaft is to be improved by hardening its surface. This is to be accomplished by increasing the nitrogen content within an outer surface layer as a result of nitrogen diffusion into the steel; the nitrogen is to be supplied from an external nitrogen-rich gas at an elevated and constant temperature. The initial nitrogen content of the steel is 0.002 Wt%, whereas the surface concentration will be maintained at 0.45 wt%. For this treatment to be effective, nitrogen content of 0.12 wt% must be established at a position 0.45 mm below the surface. Design an appropriate heat treatment in terms of temperature between 475°C and 625A°C and time Use Do = 3.0 x 10-7m2/s and Q= 76,150 J/mol.arrow_forward
- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning