is there any way to distribute ios applications outside app store?

There are several possibilities, which probably won't match your needs:

1. Since last month it's possible to test apps on a device without the need of a paid membership.
2. There's a possibility to deploy an app through a service like TestFlight, but this needs either a profile installed on the device (like HockeyApp) or always new build since the old ones expire after 30 days.
3. You could deploy an app with the Enterprise Program

The easy way you describe is not possible.

Apart from the options mentioned above there are 2 more methods.

Method 1:

You could ask the user to open a webpage in safari browser with the following link in it.

href="itms-services://?action=download-manifest&url=url of the manifest file"

The app is installed as soon as the user clicks the link.

Method 2:

You can also leverage iOS mdm solutions like Hexnode MDM though its bit of an overkill.

here is a link on how to distribute app without app store