/* --------------------------------------------------------------------- 
//  Figure 9.23:  Temperature along a cooling fin.               
//  Figure 9.22:  Fin program: the compute_temp function.             
// ---------------------------------------------------------------------
*/
#include "tools.h"

void print_table ( float N, float FinC, float WallTm, float AirTm ); 
float compute_temp( float x, float N, float FinC, float WallTm, float AirTm );

void main( void )                                                         
{   
    float len;                      /* Length of the cooling fin, in meters. */
    const float FinC = 26.5;        /* Fin constant. */
    const float WallTm = 500.0;     /* Wall temperature, degrees C. */
    const float AirTm = 20.0;       /* Air temperature, degrees C. */
                  
    banner();                                                        
    puts( " Temperature Along a Rectangular Cooling Fin" );              
    printf( " Please enter the length of the fin (m): " ); 
    scanf( "%g", &len );
    print_table( len, FinC, WallTm, AirTm );
    bye();                 
}
    
/* ------------------------------------------------------------------ 
** Print a table of temperatures for a fin that is N meters long.    
**      N must be greater than 0.                 
*/  
void 
print_table ( float N, float FinC, float WallTm, float AirTm ) 
{   
    float x;                        /* Current distance from wall. */ 
    float temp;                     /* Temperature at distance x from wall. */ 
    const float step = .005;        /* Step size for loop. */
    const float epsilon = step/2.0; /* For floating comparison to end loop. */

    printf( "\n Distance from base (m)    Temperature (C) \n" 
            " ----------------------    --------------- \n" );    
    for (x = 0.0; x < N + epsilon; x += step) {                          
        temp =  compute_temp( x, N, FinC, WallTm, AirTm );
        printf( "%12.3f %24.1f \n", x, temp );   
    }    
    printf( " ----------------------    --------------- \n" ); 
}   
    
/* ------------------------------------------------------------------  
** Compute and return the temperature at distance x from the wall.  
**     x must be between 0.0 meters and the length of the fin. 
*/
float 
compute_temp( float x, float N, float FinC, float WallTm, float AirTm )
{   
    return AirTm + (WallTm - AirTm) * cosh( FinC*(N-x) ) / cosh( FinC*N );
}