Error concatenating directory path in bash script

Tilde (~) will not be expanded by shell when put inside quotes. Just remove the quotes :

#!/bin/bash
dir_path=~/Desktop/param_bind_b
cd "$dir_path"

An other solution is, place only the ~ outside the quotes or use $HOME instead. Additionally you should add || exit behind cd.

#!/bin/bash
dir_path=~"/Desktop/param_bind_b"
cd "$dir_path" || exit

Or

#!/bin/bash
dir_path="$HOME/Desktop/param_bind_b"
cd "$dir_path" || exit

so you can use other variables, E.G.

#!/bin/bash
desktop_dir="/Desktop"
dir_path=~"$desktop_dir/param_bind_b"
cd "$dir_path" || exit

or

#!/bin/bash
desktop_dir="/Desktop"
dir_path=~"$desktop_dir"/param_bind_b
cd "$dir_path" || exit

or

#!/bin/bash
desktop_dir="/Desktop"
dir_path="$HOME$desktop_dir"/param_bind_b
cd "$dir_path" || exit

In the future, check your scripts here. ;)