For a strong feeling:
* The artist held an ardent passion for capturing the beauty of nature in her paintings.
* Despite the challenges, she remained an ardent advocate for social justice.
For intense desire:
* The young couple shared an ardent love for each other, their eyes locked in a passionate embrace.
* His ardent desire for knowledge led him to spend countless hours in the library.
For intense zeal:
* The group of volunteers displayed ardent enthusiasm as they worked tirelessly to clean up the park.
* He had an ardent belief in the power of education to transform lives.
For intense heat:
* The ardent sun beat down on the desert landscape, making it almost impossible to walk.
* The blacksmith's forge radiated ardent heat, the flames licking at the metal.
The best sentence for you depends on the specific meaning you want to convey.