ANS:B - more space.

Comparing a concentric double pipe heat exchanger to a shell and tube heat exchanger for the same heat load:

1. Less heating surface: Typically, a concentric double pipe heat exchanger would require more heating surface compared to a shell and tube heat exchanger for the same heat load. Shell and tube heat exchangers generally have a larger surface area available for heat transfer due to their design, which allows for more efficient heat transfer.
2. More space: Concentric double pipe heat exchangers are often more compact compared to shell and tube heat exchangers for the same heat load. Shell and tube heat exchangers tend to occupy more space due to their larger size and configuration.
3. Lower maintenance cost: Concentric double pipe heat exchangers generally have simpler designs with fewer components compared to shell and tube heat exchangers. This simplicity can often translate to lower maintenance costs, as there are fewer parts to inspect, clean, and repair.