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An air heater may be fabricated by coiling Nichrome wire and passing air in cross flow over the wire. Consider a heater fabricated from wire of diameter D = 1 mm, electrical resistivity pe = 106 Q-m, thermal conductivity k = 25 W/m-K, and emissivity & = 0.2. The heater is designed to deliver air at a temperature of T = 350°C under flow conditions that provide a convection coefficient of h = 350 W/m²-K for the wire. The temperature of the housing that encloses the wire and through which the air flows is Tsur = 50°C. (a) If the maximum allowable temperature of the wire is Tmax = 1200°C, what is the maximum allowable electric current I? If the maximum available voltage is AE = 110 V, what is (b) the corresponding length L of wire that may be used in the heater and (c) the power rating of the heater? Hint: In your solution, assume negligible temperature variations within the wire, but after obtaining the desired results, assess the validity of this assumption. Wire (D, L,Pe, k,&, Tmax) ↑1 -Housing, Tsur 0 0 0 0 0 0 0 - ΔΕ (a) Imax (b) L = = (c) Pelec = i i i A m kW Air Th

An air heater may be fabricated by coiling Nichrome wire and passing air in cross flow over the wire. Consider a heater fabricated from wire of diameter D = 1 mm, electrical resistivity pe = 106 Q-m, thermal conductivity k = 25 W/m-K, and emissivity & = 0.2. The heater is designed to deliver air at a temperature of T = 350°C under flow conditions that provide a convection coefficient of h = 350 W/m²-K for the wire. The temperature of the housing that encloses the wire and through which the air flows is Tsur = 50°C. (a) If the maximum allowable temperature of the wire is Tmax = 1200°C, what is the maximum allowable electric current I? If the maximum available voltage is AE = 110 V, what is (b) the corresponding length L of wire that may be used in the heater and (c) the power rating of the heater? Hint: In your solution, assume negligible temperature variations within the wire, but after obtaining the desired results, assess the validity of this assumption. Wire (D, L,Pe, k,&, Tmax) ↑1 -Housing, Tsur 0 0 0 0 0 0 0 - ΔΕ (a) Imax (b) L = = (c) Pelec = i i i A m kW Air Th

Elements Of Electromagnetics
Elements Of Electromagnetics
7th Edition
ISBN:9780190698614
Author:Sadiku, Matthew N. O.
Publisher:Sadiku, Matthew N. O.
ChapterMA: Math Assessment
Section: Chapter Questions
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An air heater may be fabricated by coiling Nichrome wire and passing air in cross flow over the wire. Consider a heater fabricated from wire of diameter D = 1 mm, electrical resistivity pe = 106 Q-m, thermal conductivity k = 25 W/m-K, and emissivity & = 0.2. The heater is designed to deliver air at a temperature of T = 350°C under flow conditions that provide a convection coefficient of h = 350 W/m²-K for the wire. The temperature of the housing that encloses the wire and through which the air flows is Tsur = 50°C. (a) If the maximum allowable temperature of the wire is Tmax = 1200°C, what is the maximum allowable electric current I? If the maximum available voltage is AE = 110 V, what is (b) the corresponding length L of wire that may be used in the heater and (c) the power rating of the heater? Hint: In your solution, assume negligible temperature variations within the wire, but after obtaining the desired results, assess the validity of this assumption. Wire (D, L,Pe, k,&, Tmax) ↑1 -Housing, Tsur 0 0 0 0 0 0 0 - ΔΕ (a) Imax (b) L = = (c) Pelec = i i i A m kW Air Th
Transcribed Image Text:An air heater may be fabricated by coiling Nichrome wire and passing air in cross flow over the wire. Consider a heater fabricated from wire of diameter D = 1 mm, electrical resistivity pe = 106 Q-m, thermal conductivity k = 25 W/m-K, and emissivity & = 0.2. The heater is designed to deliver air at a temperature of T = 350°C under flow conditions that provide a convection coefficient of h = 350 W/m²-K for the wire. The temperature of the housing that encloses the wire and through which the air flows is Tsur = 50°C. (a) If the maximum allowable temperature of the wire is Tmax = 1200°C, what is the maximum allowable electric current I? If the maximum available voltage is AE = 110 V, what is (b) the corresponding length L of wire that may be used in the heater and (c) the power rating of the heater? Hint: In your solution, assume negligible temperature variations within the wire, but after obtaining the desired results, assess the validity of this assumption. Wire (D, L,Pe, k,&, Tmax) ↑1 -Housing, Tsur 0 0 0 0 0 0 0 - ΔΕ (a) Imax (b) L = = (c) Pelec = i i i A m kW Air Th
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