Multiple Loops on a Page Without Duplicates

Is there a reason to execute the query in each individual div instead of looping the div within the query?

<?php
$my_query = new WP_Query( 'post_type=portfolio&showposts=13' ); 
while ( $my_query->have_posts() ) :
$my_query->the_post();
?>
  <div class="port1">
    <?php the_title(); ?>
  </div>
<?php endwhile; ?>

If you want to number the divs sequentially, you can use a counter:

<?php
$i=0;
$my_query = new WP_Query( 'post_type=portfolio&showposts=13' ); 
while ( $my_query->have_posts() ) :
$my_query->the_post();
?>
  <div class="port<?php echo $i++; ?>">
    <?php the_title(); ?>
  </div>
<?php endwhile; ?>