woocommerce/templates/single-product/related.php

<?php
/**
 * Related Products
 */

global $product, $woocommerce_loop, $posts_per_page, $orderby;

$related = $product->get_related(); 

if (sizeof($related)==0) return;
?>
<div class="related products"><h2><?php _e('Related Products', 'woocommerce'); ?></h2>
	<?php
		$args = array(
			'post_type'	=> 'product',
			'ignore_sticky_posts'	=> 1,
			'posts_per_page' => $posts_per_page,
			'orderby' => $orderby,
			'post__in' => $related
		);
		$args = apply_filters('woocommerce_related_products_args', $args);
		query_posts($args);
		woocommerce_get_template_part( 'loop', 'shop' );
		wp_reset_query();
	?>
</div>