Ratio of tube length to shell diameter for a shell and tube heat exchanger is

• A. 8 : 1 to 12 : 1 for both liquid-liquid and gas-gas heat exchangers.
• B. 4 : 1 to 8 : 1 for liquid-liquid exchanger.
• C. < 4 : 1 for gas-gas exchangers.
• D. both(b) & (c).